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| author | Roger Frank <rfrank@pglaf.org> | 2025-10-15 04:49:32 -0700 |
|---|---|---|
| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-15 04:49:32 -0700 |
| commit | 5cacbee4d5384b61ff4ab64c5ee8c2059720d141 (patch) | |
| tree | ec3c2c14d0fede301dd1dbc4995cb66451682cf8 /16713-h | |
Diffstat (limited to '16713-h')
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diff --git a/16713-h/16713-h.htm b/16713-h/16713-h.htm new file mode 100644 index 0000000..dabeb6f --- /dev/null +++ b/16713-h/16713-h.htm @@ -0,0 +1,22284 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <title> + The Project Gutenberg eBook of Amusements In Mathematics, by Henry Ernest Dudeney. + </title> + <style type="text/css"> +/*<![CDATA[ XML blockout */ +<!-- + p { margin-top: .75em; + text-align: justify; + margin-bottom: .75em; + } + h1,h2,h3,h4,h5,h6 { + text-align: center; /* all headings centered */ + clear: both; + } + hr { width: 33%; + margin-top: 2em; + margin-bottom: 2em; + margin-left: auto; + margin-right: auto; + clear: both; + } + + table {margin-left: auto; margin-right: auto;} + sup {font-size: smaller;} + sub {font-size: smaller; vertical-align: -.3em;} + + body{margin-left: 10%; + margin-right: 10%; + } + + + .blockquot{margin-left: 5%; margin-right: 10%;} + .pagenum {position: absolute; left: 92%; font-size: smaller; text-align: right;} /* page numbers */ + + .right {text-align: right; margin-right: 10%;} + + .bb {border-bottom: solid 2px;} + .bl {border-left: solid 2px;} + .bt {border-top: solid 2px;} + .br {border-right: solid 2px;} + .bbox {border: solid 2px;} + + .center {text-align: center;} + .smcap {font-variant: small-caps;} + .u {text-decoration: underline;} + + .su2 {font-size: smaller; vertical-align: .5em} + + + .caption {font-weight: bold;} + + .figcenter {margin: auto; text-align: center;} + + .figleft {float: left; clear: left; margin-left: 0; margin-bottom: 1em; margin-top: + 1em; margin-right: 1em; padding: 0; text-align: center;} + + .figright {float: right; clear: right; margin-left: 1em; margin-bottom: 1em; + margin-top: 1em; margin-right: 0; padding: 0; text-align: center;} + + .poem {margin-left:10%; margin-right:10%; text-align: left; padding-left: 3em; text-indent: -3em;} + .poem br {display: none;} + .poem .stanza {margin: 1em 0em 1em 0em;} + .poem span.i0 {display: block; margin-left: 0em;} + .poem span.i2 {display: block; margin-left: 2em;} + .poem span.i4 {display: block; margin-left: 4em;} + .poem span.i8 {display: block; margin-left: 8em;} + + // --> + /* XML end ]]>*/ + </style> + </head> +<body> + + +<pre> + +Project Gutenberg's Amusements in Mathematics, by Henry Ernest Dudeney + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Amusements in Mathematics + +Author: Henry Ernest Dudeney + +Release Date: September 17, 2005 [EBook #16713] +[Most recently updated: October 28, 2018] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK AMUSEMENTS IN MATHEMATICS *** + + + + +Produced by Stephen Schulze, Jonathan Ingram and the Online +Distributed Proofreading Team at https://www.pgdp.net + + + + + + +</pre> + + +<div style="background: #EEEEEE; padding: 2em; border: dashed 1px;"><p>Transcribers note: Many of the puzzles in this book assume a +familiarity with the currency of Great Britain in the early 1900s. As +this is likely not common knowledge for those outside Britain (and possibly +many within,) I am including a chart of relative values.</p> + +<p>The most common units used were:</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>the Penny,</td><td align='left'>abbreviated: <i>d</i>. (from the Roman penny, denarius)</td></tr> +<tr><td align='left'>the Shilling,</td><td align='left'>abbreviated: <i>s</i>.</td></tr> +<tr><td align='left'>the Pound,</td><td align='left'>abbreviated: £</td></tr> +</table></div> + +<p>There was 12 Pennies to a Shilling and 20 Shillings to a Pound, so there +was 240 Pennies in a Pound.</p> + +<p>To further complicate things, there were many coins which were various +fractional values of Pennies, Shillings or Pounds.</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Farthing</td><td align='right'>¼<i>d</i>.</td></tr> +<tr><td align='left'>Half-penny</td><td align='right'>½<i>d</i>.</td></tr> +<tr><td align='left'>Penny</td><td align='right'>1<i>d</i>.</td></tr> +<tr><td align='left'>Three-penny</td><td align='right'>3<i>d</i>.</td></tr> +<tr><td align='left'>Sixpence (or tanner)</td><td align='right'>6<i>d</i>.</td></tr> +<tr><td align='left'>Shilling (or bob)</td><td align='right'>1<i>s</i>.</td></tr> +<tr><td align='left'>Florin or two shilling piece</td><td align='right'>2<i>s</i>.</td></tr> +<tr><td align='left'>Half-crown (or half-dollar)</td><td align='right'>2<i>s</i>. 6<i>d</i>.</td></tr> +<tr><td align='left'>Double-florin</td><td align='right'>4<i>s</i>.</td></tr> +<tr><td align='left'>Crown (or dollar)</td><td align='right'>5<i>s</i>.</td></tr> +<tr><td align='left'>Half-Sovereign</td><td align='right'>10<i>s</i>.</td></tr> +<tr><td align='left'>Sovereign (or Pound)</td><td align='right'>£1 or 20<i>s</i>.</td></tr> +</table></div> + +<p>This is by no means a comprehensive list, but it should be adequate to +solve the puzzles in this book.</p></div> + + + + +<h1>AMUSEMENTS IN MATHEMATICS</h1> + +<h4><i>by</i></h4> + +<h2>HENRY ERNEST DUDENEY</h2> + +<table summary=''><tr><td> +<div class="poem center"><div class="stanza"> +<span class="i0">In Mathematicks he was greater<br /></span> +<span class="i0">Than Tycho Brahe or Erra Pater:<br /></span> +<span class="i0">For he, by geometrick scale,<br /></span> +<span class="i0">Could take the size of pots of ale;<br /></span> +<span class="i0">Resolve, by sines and tangents, straight,<br /></span> +<span class="i0">If bread or butter wanted weight;<br /></span> +<span class="i0">And wisely tell what hour o' th' day<br /></span> +<span class="i0">The clock does strike by algebra.<br /></span> +</div><div class="stanza"> +<span class="i8">BUTLER'S <i>Hudibras</i>.<br /></span> +</div></div> +</td></tr></table> + + +<h5>1917</h5> + +<hr style="width: 65%;" /><p><span class='pagenum'>Pg v<a name="Page_v" id="Page_v"></a></span></p> +<h2><a name="PREFACE" id="PREFACE"></a>PREFACE</h2> + +<p>In issuing this volume of my Mathematical Puzzles, of which some have +appeared in periodicals and others are given here for the first time, +I must acknowledge the encouragement that I have received from many +unknown correspondents, at home and abroad, who have expressed a +desire to have the problems in a collected form, with some of the +solutions given at greater length than is possible in magazines and +newspapers. Though I have included a few old puzzles that have +interested the world for generations, where I felt that there was +something new to be said about them, the problems are in the main +original. It is true that some of these have become widely known +through the press, and it is possible that the reader may be glad to +know their source.</p> + +<p>On the question of Mathematical Puzzles in general there is, perhaps, +little more to be said than I have written elsewhere. The history of +the subject entails nothing short of the actual story of the +beginnings and development of exact thinking in man. The historian +must start from the time when man first succeeded in counting his ten +fingers and in dividing an apple into two approximately equal parts. +Every puzzle that is worthy of consideration can be referred to +mathematics and logic. Every man, woman, and child who tries to +"reason out" the answer to the simplest puzzle is working, though not +of necessity consciously, on mathematical lines. Even those puzzles +that we have no way of attacking except by haphazard attempts can be +brought under a method of what has been called "glorified trial"—a +system of shortening our labours by avoiding or eliminating what our +reason tells us is useless. It is, in fact, not easy to say sometimes +where the "empirical" begins and where it ends.</p> + +<p>When a man says, "I have never solved a puzzle in my life," it is +difficult to know exactly what he means, for every intelligent +individual is doing it every day. The unfortunate inmates of our +lunatic asylums are sent there expressly because they cannot solve +puzzles—because they have lost their powers of reason. If there were +no puzzles to solve, there would be no questions to ask; and if there +were no questions to be asked, what a world it would be! We should all +be equally omniscient, and conversation would be useless and idle.</p> + +<p>It is possible that some few exceedingly sober-minded mathematicians, +who are impatient of any terminology in their favourite science but +the academic, and who object to the elusive <i>x</i> and <i>y</i> appearing +under any other names, will have wished that various problems had +been presented in a less popular dress and introduced with a less +flippant phraseology. I can only refer them to the first word of my +title and remind them that we are primarily out to be amused—not, it +is true, without some hope of picking up morsels of knowledge by the +way. If the manner is light, I can only say, in the words of +Touchstone, that it is "an ill-favoured thing, sir, but my own; a poor +humour of mine, sir."</p> + +<p>As for the question of difficulty, some of the puzzles, especially in +the Arithmetical and Algebraical category, are quite easy. Yet some of +those examples that look the simplest should not be passed over +without a little consideration, for now and again it will be found +that there is some more or less subtle pitfall or trap into which the +reader may be apt to fall. It is good exercise to cultivate the habit +of being very wary over the exact wording of a puzzle. It teaches +exactitude and caution. But some of the problems are very hard nuts +indeed, and not unworthy of the attention of the advanced +mathematician. Readers will doubtless select according to their +individual tastes.</p> + +<p>In many cases only the mere answers are given. This leaves the +beginner something to do on his own behalf in working out the method +of solution, and saves space that would be wasted from the point of +view of the advanced student. On the other hand, in particular cases +where it seemed likely to interest, I have given rather extensive +solutions and treated problems in a general manner. It will often be +found that the notes on one problem will serve to elucidate a good +many others in the book; so that the reader's difficulties will +sometimes be found cleared up as he advances. Where it is possible to +say a thing in a manner that may be "understanded of the people" +generally, I prefer to use this simple phraseology, and so engage the +attention and interest of a larger public. The mathematician will in +such cases have no difficulty in expressing the matter under +consideration in terms of his familiar symbols.</p> + +<p>I have taken the greatest care in reading the proofs, and trust that +any errors that may have crept in are very few. If any such should +occur, I can only plead, in the words of Horace, that "good Homer +sometimes nods," or, as the bishop put it, "Not even the youngest +curate in my diocese is infallible."</p> + +<p>I have to express my thanks in particular to the proprietors of <i>The +Strand Magazine</i>, <i>Cassell's Magazine</i>, <i>The Queen</i>, <i>Tit-Bits</i>, and +<i>The Weekly Dispatch</i> for their courtesy in allowing me to reprint +some of the puzzles that have appeared in their pages.</p> + +<p class='right'>THE AUTHORS' CLUB<br/> +<i>March</i> 25, 1917</p> + +<hr style="width: 65%;" /> +<h2><a name="CONTENTS" id="CONTENTS"></a>CONTENTS</h2> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'><a href="#PREFACE"><b>PREFACE</b></a></td><td align='right'><a href="#Page_v">v</a></td></tr> +<tr><td align='left'><a href="#ARITHMETICAL_AND_ALGEBRAICAL_PROBLEMS"><b>ARITHMETICAL AND ALGEBRAICAL PROBLEMS.</b></a></td><td align='right'><a href="#Page_1">1</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#MONEY_PUZZLES"><b>Money Puzzles.</b></a></span></td><td align='right'><a href="#Page_1">1</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#AGE_AND_KINSHIP_PUZZLES"><b>Age and Kinship Puzzles.</b></a></span></td><td align='right'><a href="#Page_6">6</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#CLOCK_PUZZLES"><b>Clock Puzzles.</b></a></span></td><td align='right'><a href="#Page_9">9</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#LOCOMOTION_AND_SPEED_PUZZLES"><b>Locomotion and Speed Puzzles.</b></a></span></td><td align='right'><a href="#Page_11">11</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#DIGITAL_PUZZLES"><b>Digital Puzzles.</b></a></span></td><td align='right'><a href="#Page_13">13</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#VARIOUS_ARITHMETICAL_AND_ALGEBRAICAL_PROBLEMS"><b>Various Arithmetical and Algebraical Problems.</b></a></span></td><td align='right'><a href="#Page_17">17</a></td></tr> +<tr><td align='left'><a href="#GEOMETRICAL_PROBLEMS"><b>GEOMETRICAL PROBLEMS.</b></a></td><td align='right'><a href="#Page_27">27</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#DISSECTION_PUZZLES"><b>Dissection Puzzles.</b></a></span></td><td align='right'><a href="#Page_27">27</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#GREEK_CROSS_PUZZLES"><b>Greek Cross Puzzles.</b></a></span></td><td align='right'><a href="#Page_28">28</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#VARIOUS_DISSECTION_PUZZLES"><b>Various Dissection Puzzles.</b></a></span></td><td align='right'><a href="#Page_35">35</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#PATCHWORK_PUZZLES"><b>Patchwork Puzzles</b></a></span></td><td align='right'><a href="#Page_46">46</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#VARIOUS_GEOMETRICAL_PUZZLES"><b>Various Geometrical Puzzles.</b></a></span></td><td align='right'><a href="#Page_49">49</a></td></tr> +<tr><td align='left'><a href="#POINTS_AND_LINES_PROBLEMS"><b>POINTS AND LINES PROBLEMS.</b></a></td><td align='right'><a href="#Page_56">56</a></td></tr> +<tr><td align='left'><a href="#MOVING_COUNTER_PROBLEMS"><b>MOVING COUNTER PROBLEMS.</b></a></td><td align='right'><a href="#Page_58">58</a></td></tr> +<tr><td align='left'><a href="#UNICURSAL_AND_ROUTE_PROBLEMS"><b>UNICURSAL AND ROUTE PROBLEMS.</b></a></td><td align='right'><a href="#Page_68">68</a></td></tr> +<tr><td align='left'><a href="#COMBINATION_AND_GROUP_PROBLEMS"><b>COMBINATION AND GROUP PROBLEMS.</b></a></td><td align='right'><a href="#Page_76">76</a></td></tr> +<tr><td align='left'><a href="#CHESSBOARD_PROBLEMS"><b>CHESSBOARD PROBLEMS.</b></a></td><td align='right'><a href="#Page_85">85</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#THE_CHESSBOARD"><b>The Chessboard.</b></a></span></td><td align='right'><a href="#Page_85">85</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#STATICAL_CHESS_PUZZLES"><b>Statical Chess Puzzles.</b></a></span></td><td align='right'><a href="#Page_88">88</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#THE_GUARDED_CHESSBOARD"><b>The Guarded Chessboard.</b></a></span></td><td align='right'><a href="#Page_95">95</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#DYNAMICAL_CHESS_PUZZLES"><b>Dynamical Chess Puzzles.</b></a></span></td><td align='right'><a href="#Page_96">96</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#VARIOUS_CHESS_PUZZLES"><b>Various Chess Puzzles.</b></a></span></td><td align='right'><a href="#Page_112">112</a></td></tr> +<tr><td align='left'><a href="#MEASURING_WEIGHING_AND_PACKING_PUZZLES"><b>MEASURING, WEIGHING, AND PACKING PUZZLES.</b></a></td><td align='right'><a href="#Page_109">109</a></td></tr> +<tr><td align='left'><a href="#CROSSING_RIVER_PROBLEMS"><b>CROSSING RIVER PROBLEMS</b></a></td><td align='right'><a href="#Page_112">112</a></td></tr> +<tr><td align='left'><a href="#PROBLEMS_CONCERNING_GAMES"><b>PROBLEMS CONCERNING GAMES.</b></a></td><td align='right'><a href="#Page_114">114</a></td></tr> +<tr><td align='left'><a href="#PUZZLE_GAMES"><b>PUZZLE GAMES.</b></a></td><td align='right'><a href="#Page_117">117</a></td></tr> +<tr><td align='left'><a href="#MAGIC_SQUARE_PROBLEMS"><b>MAGIC SQUARE PROBLEMS.</b></a></td><td align='right'><a href="#Page_119">119</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#SUBTRACTING_MULTIPLYING_AND_DIVIDING_MAGICS"><b>Subtracting, Multiplying, and Dividing Magics.</b></a></span></td><td align='right'><a href="#Page_124">124</a></td></tr> +<tr><td align='left'><span style="margin-left: 2em;"><a href="#MAGIC_SQUARES_OF_PRIMES"><b>Magic Squares of Primes.</b></a></span></td><td align='right'><a href="#Page_125">125</a></td></tr> +<tr><td align='left'><a href="#MAZES_AND_HOW_TO_THREAD_THEM"><b>MAZES AND HOW TO THREAD THEM.</b></a></td><td align='right'><a href="#Page_127">127</a></td></tr> +<tr><td align='left'><a href="#THE_PARADOX_PARTY"><b>THE PARADOX PARTY.</b></a></td><td align='right'><a href="#Page_137">137</a></td></tr> +<tr><td align='left'><a href="#UNCLASSIFIED_PROBLEMS"><b>UNCLASSIFIED PROBLEMS.</b></a></td><td align='right'><a href="#Page_142">142</a></td></tr> +<tr><td align='left'><a href="#SOLUTIONS"><b>SOLUTIONS.</b></a></td><td align='right'><a href="#Page_148">148</a></td></tr> +<tr><td align='left'><a href="#INDEX"><b>INDEX.</b></a></td><td align='right'><a href="#Page_253">253</a></td></tr> +</table></div> + +<hr style="width: 65%;" /><p><span class='pagenum'>Pg 1<a name="Page_1" id="Page_1"></a></span></p> +<h1>AMUSEMENTS IN MATHEMATICS.</h1> + + +<hr style="width: 65%;" /> +<h2><a name="ARITHMETICAL_AND_ALGEBRAICAL_PROBLEMS" id="ARITHMETICAL_AND_ALGEBRAICAL_PROBLEMS"></a><a href="#CONTENTS">ARITHMETICAL AND ALGEBRAICAL PROBLEMS.</a></h2> + +<p class='center'> +<span style="margin-left: 7em;">"And what was he?</span><br /> +<span style="margin-left: 0em;">Forsooth, a great arithmetician."</span><br /> +<span style="margin-left: 10em;"><i>Othello</i>, I. i.</span><br /> +</p> + +<p>The puzzles in this department are roughly thrown together in classes +for the convenience of the reader. Some are very easy, others quite +difficult. But they are not arranged in any order of difficulty—and +this is intentional, for it is well that the solver should not be +warned that a puzzle is just what it seems to be. It may, therefore, +prove to be quite as simple as it looks, or it may contain some +pitfall into which, through want of care or over-confidence, we may +stumble.</p> + +<p>Also, the arithmetical and algebraical puzzles are not separated in +the manner adopted by some authors, who arbitrarily require certain +problems to be solved by one method or the other. The reader is left +to make his own choice and determine which puzzles are capable of +being solved by him on purely arithmetical lines.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="MONEY_PUZZLES" id="MONEY_PUZZLES"></a><a href="#CONTENTS">MONEY PUZZLES.</a></h2> + +<p class='center'> +<span style="margin-left: 0em;">"Put not your trust in money, but put your money in trust."<br /></span> +<span style="margin-left: 10em;">OLIVER WENDELL HOLMES.<br /></span> +</p> + +<hr style="width: 30%;" /> +<p><a name="X_1_A_POST-OFFICE_PERPLEXITY" id="X_1_A_POST-OFFICE_PERPLEXITY"></a><a href="#X_1_A_POST-OFFICE_PERPLEXITYa"><b>1.—A POST-OFFICE PERPLEXITY.</b></a></p> + +<p>In every business of life we are occasionally perplexed by some chance +question that for the moment staggers us. I quite pitied a young lady +in a branch post-office when a gentleman entered and deposited a crown +on the counter with this request: "Please give me some twopenny +stamps, six times as many penny stamps, and make up the rest of the +money in twopence-halfpenny stamps." For a moment she seemed +bewildered, then her brain cleared, and with a smile she handed over +stamps in exact fulfilment of the order. How long would it have taken +you to think it out?</p> + +<hr style="width: 30%;" /> +<p><a name="X_2_YOUTHFUL_PRECOCITY" id="X_2_YOUTHFUL_PRECOCITY"></a><a href="#X_2_YOUTHFUL_PRECOCITYa"><b>2.—YOUTHFUL PRECOCITY.</b></a></p> + +<p>The precocity of some youths is surprising. One is disposed to say on +occasion, "That boy of yours is a genius, and he is certain to do +great things when he grows up;" but past experience has taught us that +he invariably becomes quite an ordinary citizen. It is so often the +case, on the contrary, that the dull boy becomes a great man. You +never can tell. Nature loves to present to us these queer paradoxes. +It is well known that those wonderful "lightning calculators," who now +and again surprise the world by their feats, lose all their mysterious +powers directly they are taught the elementary rules of arithmetic.</p> + +<p>A boy who was demolishing a choice banana was approached by a young +friend, who, regarding him with envious eyes, asked, "How much did you +pay for that banana, Fred?" The prompt answer was quite remarkable in +its way: "The man what I bought it of receives just half as many +sixpences for sixteen dozen dozen bananas as he gives bananas for a +fiver."</p> + +<p>Now, how long will it take the reader to say correctly just how much +Fred paid for his rare and refreshing fruit?</p> + +<hr style="width: 30%;" /> +<p><a name="X_3_AT_A_CATTLE_MARKET" id="X_3_AT_A_CATTLE_MARKET"></a><a href="#X_3_AT_A_CATTLE_MARKETa"><b>3.—AT A CATTLE MARKET.</b></a></p> + +<p>Three countrymen met at a cattle market. "Look here," said Hodge to +Jakes, "I'll give you six of my pigs for one of your horses, and then +you'll have twice as many animals here as I've got." "If that's your +way of doing business," said Durrant to Hodge, "I'll give you fourteen +of my sheep for a horse, and then you'll have three times as many +animals as I." "Well, I'll go better than that," said Jakes to +Durrant; "I'll give you four cows for a horse, <span class='pagenum'>Pg 2<a name="Page_2" id="Page_2"></a></span>and then you'll have +six times as many animals as I've got here."</p> + +<p>No doubt this was a very primitive way of bartering animals, but it is +an interesting little puzzle to discover just how many animals Jakes, +Hodge, and Durrant must have taken to the cattle market.</p> + +<hr style="width: 30%;" /> +<p><a name="X_4_THE_BEANFEAST_PUZZLE" id="X_4_THE_BEANFEAST_PUZZLE"></a><a href="#X_4_THE_BEANFEAST_PUZZLEa"><b>4.—THE BEANFEAST PUZZLE.</b></a></p> + +<p>A number of men went out together on a bean-feast. There were four +parties invited—namely, 25 cobblers, 20 tailors, 18 hatters, and 12 +glovers. They spent altogether £6, 13<i>s</i>. It was found that five +cobblers spent as much as four tailors; that twelve tailors spent as +much as nine hatters; and that six hatters spent as much as eight +glovers. The puzzle is to find out how much each of the four parties +spent.</p> + +<hr style="width: 30%;" /> +<p><a name="X_5_A_QUEER_COINCIDENCE" id="X_5_A_QUEER_COINCIDENCE"></a><a href="#X_5_A_QUEER_COINCIDENCEa"><b>5.—A QUEER COINCIDENCE.</b></a></p> + +<p>Seven men, whose names were Adams, Baker, Carter, Dobson, Edwards, +Francis, and Gudgeon, were recently engaged in play. The name of the +particular game is of no consequence. They had agreed that whenever a +player won a game he should double the money of each of the other +players—that is, he was to give the players just as much money as +they had already in their pockets. They played seven games, and, +strange to say, each won a game in turn, in the order in which their +names are given. But a more curious coincidence is this—that when +they had finished play each of the seven men had exactly the same +amount—two shillings and eightpence—in his pocket. The puzzle is to +find out how much money each man had with him before he sat down to +play.</p> + +<hr style="width: 30%;" /> +<p><a name="X_6_A_CHARITABLE_BEQUEST" id="X_6_A_CHARITABLE_BEQUEST"></a><a href="#X_6_A_CHARITABLE_BEQUESTa"><b>6.—A CHARITABLE BEQUEST.</b></a></p> + +<p>A man left instructions to his executors to distribute once a year +exactly fifty-five shillings among the poor of his parish; but they +were only to continue the gift so long as they could make it in +different ways, always giving eighteenpence each to a number of women +and half a crown each to men. During how many years could the charity +be administered? Of course, by "different ways" is meant a different +number of men and women every time.</p> + +<hr style="width: 30%;" /> +<p><a name="X_7_THE_WIDOWS_LEGACY" id="X_7_THE_WIDOWS_LEGACY"></a><a href="#X_7_THE_WIDOWS_LEGACYa"><b>7.—THE WIDOW'S LEGACY.</b></a></p> + +<p>A gentleman who recently died left the sum of £8,000 to be divided +among his widow, five sons, and four daughters. He directed that every +son should receive three times as much as a daughter, and that every +daughter should have twice as much as their mother. What was the +widow's share?</p> + +<hr style="width: 30%;" /> +<p><a name="X_8_INDISCRIMINATE_CHARITY" id="X_8_INDISCRIMINATE_CHARITY"></a><a href="#X_8_INDISCRIMINATE_CHARITYa"><b>8.—INDISCRIMINATE CHARITY.</b></a></p> + +<p>A charitable gentleman, on his way home one night, was appealed to by +three needy persons in succession for assistance. To the first person +he gave one penny more than half the money he had in his pocket; to +the second person he gave twopence more than half the money he then +had in his pocket; and to the third person he handed over threepence +more than half of what he had left. On entering his house he had only +one penny in his pocket. Now, can you say exactly how much money that +gentleman had on him when he started for home?</p> + +<hr style="width: 30%;" /> +<p><a name="X_9_THE_TWO_AEROPLANES" id="X_9_THE_TWO_AEROPLANES"></a><a href="#X_9_THE_TWO_AEROPLANESa"><b>9.—THE TWO AEROPLANES.</b></a></p> + +<p>A man recently bought two aeroplanes, but afterwards found that they +would not answer the purpose for which he wanted them. So he sold them +for £600 each, making a loss of 20 per cent, on one machine and a +profit of 20 per cent, on the other. Did he make a profit on the whole +transaction, or a loss? And how much?</p> + +<hr style="width: 30%;" /> +<p><a name="X_10_BUYING_PRESENTS" id="X_10_BUYING_PRESENTS"></a><a href="#X_10_BUYING_PRESENTSa"><b>10.—BUYING PRESENTS.</b></a></p> + +<p>"Whom do you think I met in town last week, Brother William?" said +Uncle Benjamin. "That old skinflint Jorkins. His family had been +taking him around buying Christmas presents. He said to me, 'Why +cannot the government abolish Christmas, and make the giving of +presents punishable by law? I came out this morning with a certain +amount of money in my pocket, and I find I have spent just half of it. +In fact, if you will believe me, I take home just as many shillings as +I had pounds, and half as many pounds as I had shillings. It is +monstrous!'" Can you say exactly how much money Jorkins had spent on +those presents?</p> + +<hr style="width: 30%;" /> +<p><a name="X_11_THE_CYCLISTS_FEAST" id="X_11_THE_CYCLISTS_FEAST"></a><a href="#X_11_THE_CYCLISTS_FEASTa"><b>11.—THE CYCLISTS' FEAST.</b></a></p> + +<div class="poem"><div class="stanza"> +<span class="i0">'Twas last Bank Holiday, so I've been told,<br /></span> +<span class="i2">Some cyclists rode abroad in glorious weather.<br /></span> +<span class="i0">Resting at noon within a tavern old,<br /></span> +<span class="i2">They all agreed to have a feast together.<br /></span> +<span class="i0">"Put it all in one bill, mine host," they said,<br /></span> +<span class="i2">"For every man an equal share will pay."<br /></span> +<span class="i0">The bill was promptly on the table laid,<br /></span> +<span class="i2">And four pounds was the reckoning that day.<br /></span> +<span class="i0">But, sad to state, when they prepared to square,<br /></span> +<span class="i2">'Twas found that two had sneaked outside and fled.<br /></span> +<span class="i0">So, for two shillings more than his due share<br /></span> +<span class="i2">Each honest man who had remained was bled.<br /></span> +<span class="i0">They settled later with those rogues, no doubt.<br /></span> +<span class="i2">How many were they when they first set out?<br /></span> +</div></div> + +<hr style="width: 30%;" /> +<p><a name="X_12_A_QUEER_THING_IN_MONEY" id="X_12_A_QUEER_THING_IN_MONEY"></a><a href="#X_12_A_QUEER_THING_IN_MONEYa"><b>12.—A QUEER THING IN MONEY.</b></a></p> + +<p>It will be found that £66, 6<i>s</i>. 6<i>d</i>. equals 15,918 pence. Now, the four +6's added together make 24, and the figures in 15,918 also add to 24. +It is a curious fact that there is only one other sum of money, in +pounds, shillings, and pence (all similarly repetitions of one +figure), of which the digits shall add up the same as the digits of +the amount in pence. What is the other sum of money?</p> + +<hr style="width: 30%;" /> +<p><a name="X_13_A_NEW_MONEY_PUZZLE" id="X_13_A_NEW_MONEY_PUZZLE"></a><a href="#X_13_A_NEW_MONEY_PUZZLEa"><b>13.—A NEW MONEY PUZZLE.</b></a></p> + +<p>The largest sum of money that can be written in pounds, shillings, +pence, and farthings, using each of the nine digits once and only +once, is <span class='pagenum'>Pg 3<a name="Page_3" id="Page_3"></a></span>£98,765, 4<i>s</i>. 3½<i>d</i>. Now, try to discover the smallest sum +of money that can be written down under precisely the same conditions. +There must be some value given for each denomination—pounds, +shillings, pence, and farthings—and the nought may not be used. It +requires just a little judgment and thought.</p> + +<hr style="width: 30%;" /> +<p><a name="X_14_SQUARE_MONEY" id="X_14_SQUARE_MONEY"></a><a href="#X_14_SQUARE_MONEYa"><b>14.—SQUARE MONEY.</b></a></p> + +<p>"This is queer," said McCrank to his friend. "Twopence added to +twopence is fourpence, and twopence multiplied by twopence is also +fourpence." Of course, he was wrong in thinking you can multiply money +by money. The multiplier must be regarded as an abstract number. It is +true that two feet multiplied by two feet will make four square feet. +Similarly, two pence multiplied by two pence will produce four square +pence! And it will perplex the reader to say what a "square penny" is. +But we will assume for the purposes of our puzzle that twopence +multiplied by twopence is fourpence. Now, what two amounts of money +will produce the next smallest possible result, the same in both +cases, when added or multiplied in this manner? The two amounts need +not be alike, but they must be those that can be paid in current coins +of the realm.</p> + +<hr style="width: 30%;" /> +<p><a name="X_15_POCKET_MONEY" id="X_15_POCKET_MONEY"></a><a href="#X_15_POCKET_MONEYa"><b>15.—POCKET MONEY.</b></a></p> + +<p>What is the largest sum of money—all in current silver coins and no +four-shilling piece—that I could have in my pocket without being able +to give change for a half-sovereign?</p> +<hr style="width: 30%;" /> +<p><a name="X_16_THE_MILLIONAIRES_PERPLEXITY" id="X_16_THE_MILLIONAIRES_PERPLEXITY"></a><a href="#X_16_THE_MILLIONAIRES_PERPLEXITYa"><b>16.—THE MILLIONAIRE'S PERPLEXITY.</b></a></p> + +<p>Mr. Morgan G. Bloomgarten, the millionaire, known in the States as the +Clam King, had, for his sins, more money than he knew what to do with. +It bored him. So he determined to persecute some of his poor but happy +friends with it. They had never done him any harm, but he resolved to +inoculate them with the "source of all evil." He therefore proposed to +distribute a million dollars among them and watch them go rapidly to +the bad. But he was a man of strange fancies and superstitions, and it +was an inviolable rule with him never to make a gift that was not +either one dollar or some power of seven—such as 7, 49, 343, 2,401, +which numbers of dollars are produced by simply multiplying sevens +together. Another rule of his was that he would never give more than +six persons exactly the same sum. Now, how was he to distribute the +1,000,000 dollars? You may distribute the money among as many people +as you like, under the conditions given.</p> +<hr style="width: 30%;" /> +<p><a name="X_17_THE_PUZZLING_MONEY_BOXES" id="X_17_THE_PUZZLING_MONEY_BOXES"></a><a href="#X_17_THE_PUZZLING_MONEY_BOXESa"><b>17.—THE PUZZLING MONEY-BOXES.</b></a></p> + +<p>Four brothers—named John, William, Charles, and Thomas—had each a +money-box. The boxes were all given to them on the same day, and they +at once put what money they had into them; only, as the boxes were not +very large, they first changed the money into as few coins as +possible. After they had done this, they told one another how much +money they had saved, and it was found that if John had had 2<i>s</i>. more +in his box than at present, if William had had 2<i>s</i>. less, if Charles +had had twice as much, and if Thomas had had half as much, they would +all have had exactly the same amount.</p> + +<p>Now, when I add that all four boxes together contained 45<i>s</i>., and that +there were only six coins in all in them, it becomes an entertaining +puzzle to discover just what coins were in each box.</p> + +<hr style="width: 30%;" /> +<p><a name="X_18_THE_MARKET_WOMEN" id="X_18_THE_MARKET_WOMEN"></a><a href="#X_18_THE_MARKET_WOMENa"><b>18.—THE MARKET WOMEN.</b></a></p> + +<p>A number of market women sold their various products at a certain +price per pound (different in every case), and each received the same +amount—2<i>s</i>. 2½d. What is the greatest number of women there could +have been? The price per pound in every case must be such as could be +paid in current money.</p> + +<hr style="width: 30%;" /> +<p><a name="X_19_THE_NEW_YEARS_EVE_SUPPERS" id="X_19_THE_NEW_YEARS_EVE_SUPPERS"></a><a href="#X_19_THE_NEW_YEARS_EVE_SUPPERSa"><b>19.—THE NEW YEAR'S EVE SUPPERS.</b></a></p> + +<p>The proprietor of a small London café has given me some interesting +figures. He says that the ladies who come alone to his place for +refreshment spend each on an average eighteenpence, that the +unaccompanied men spend half a crown each, and that when a gentleman +brings in a lady he spends half a guinea. On New Year's Eve he +supplied suppers to twenty-five persons, and took five pounds in all. +Now, assuming his averages to have held good in every case, how was +his company made up on that occasion? Of course, only single +gentlemen, single ladies, and pairs (a lady and gentleman) can be +supposed to have been present, as we are not considering larger +parties.</p> + +<hr style="width: 30%;" /> +<p><a name="X_20_BEEF_AND_SAUSAGES" id="X_20_BEEF_AND_SAUSAGES"></a><a href="#X_20_BEEF_AND_SAUSAGESa"><b>20.—BEEF AND SAUSAGES.</b></a></p> + +<p>"A neighbour of mine," said Aunt Jane, "bought a certain quantity of +beef at two shillings a pound, and the same quantity of sausages at +eighteenpence a pound. I pointed out to her that if she had divided +the same money equally between beef and sausages she would have gained +two pounds in the total weight. Can you tell me exactly how much she +spent?"</p> + +<p>"Of course, it is no business of mine," said Mrs. Sunniborne; "but a +lady who could pay such prices must be somewhat inexperienced in +domestic economy."</p> + +<p>"I quite agree, my dear," Aunt Jane replied, "but you see that is not +the precise point under discussion, any more than the name and morals +of the tradesman."</p> + +<hr style="width: 30%;" /> +<p><a name="X_21_A_DEAL_IN_APPLES" id="X_21_A_DEAL_IN_APPLES"></a><a href="#X_21_A_DEAL_IN_APPLESa"><b>21.—A DEAL IN APPLES.</b></a></p> + +<p>I paid a man a shilling for some apples, but they were so small that I +made him throw in two extra apples. I find that made them cost just a +penny a dozen less than the first price he asked. How many apples did +I get for my shilling?</p> + +<hr style="width: 30%;" /> +<p><a name="X_22_A_DEAL_IN_EGGS" id="X_22_A_DEAL_IN_EGGS"></a><a href="#X_22_A_DEAL_IN_EGGSa"><b>22.—A DEAL IN EGGS.</b></a></p> + +<p>A man went recently into a dairyman's shop to buy eggs. He wanted them +of various qualities. <span class='pagenum'>Pg 4<a name="Page_4" id="Page_4"></a></span>The salesman had new-laid eggs at the high +price of fivepence each, fresh eggs at one penny each, eggs at a +halfpenny each, and eggs for electioneering purposes at a greatly +reduced figure, but as there was no election on at the time the buyer +had no use for the last. However, he bought some of each of the three +other kinds and obtained exactly one hundred eggs for eight and +fourpence. Now, as he brought away exactly the same number of eggs of +two of the three qualities, it is an interesting puzzle to determine +just how many he bought at each price.</p> + +<hr style="width: 30%;" /> +<p><a name="X_23_THE_CHRISTMAS-BOXES" id="X_23_THE_CHRISTMAS-BOXES"></a><a href="#X_23_THE_CHRISTMAS-BOXESa"><b>23.—THE CHRISTMAS-BOXES.</b></a></p> + +<p>Some years ago a man told me he had spent one hundred English silver +coins in Christmas-boxes, giving every person the same amount, and it +cost him exactly £1, 10<i>s</i>. 1<i>d</i>. Can you tell just how many persons +received the present, and how he could have managed the distribution? +That odd penny looks queer, but it is all right.</p> + +<hr style="width: 30%;" /> +<p><a name="X_24_A_SHOPPING_PERPLEXITY" id="X_24_A_SHOPPING_PERPLEXITY"></a><a href="#X_24_A_SHOPPING_PERPLEXITYa"><b>24.—A SHOPPING PERPLEXITY.</b></a></p> + +<p>Two ladies went into a shop where, through some curious eccentricity, +no change was given, and made purchases amounting together to less +than five shillings. "Do you know," said one lady, "I find I shall +require no fewer than six current coins of the realm to pay for what I +have bought." The other lady considered a moment, and then exclaimed: +"By a peculiar coincidence, I am exactly in the same dilemma." "Then +we will pay the two bills together." But, to their astonishment, they +still required six coins. What is the smallest possible amount of +their purchases—both different?</p> + +<hr style="width: 30%;" /> +<p><a name="X_25_CHINESE_MONEY" id="X_25_CHINESE_MONEY"></a><a href="#X_25_CHINESE_MONEYa"><b>25.—CHINESE MONEY.</b></a></p> + +<p>The Chinese are a curious people, and have strange inverted ways of +doing things. It is said that they use a saw with an upward pressure +instead of a downward one, that they plane a deal board by pulling the +tool toward them instead of pushing it, and that in building a house +they first construct the roof and, having raised that into position, +proceed to work downwards. In money the currency of the country +consists of taels of fluctuating value. The tael became thinner and +thinner until 2,000 of them piled together made less than three inches +in height. The common cash consists of brass coins of varying +thicknesses, with a round, square, or triangular hole in the centre, +as in our illustration.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q025.png" width="400" height="134" alt="" title="" /> +</div> + +<p>These are strung on wires like buttons. Supposing that eleven coins +with round holes are worth fifteen ching-changs, that eleven with +square holes are worth sixteen ching-changs, and that eleven with +triangular holes are worth seventeen ching-changs, how can a Chinaman +give me change for half a crown, using no coins other than the three +mentioned? A ching-chang is worth exactly twopence and four-fifteenths +of a ching-chang.</p> + +<hr style="width: 30%;" /> +<p><a name="X_26_THE_JUNIOR_CLERKS_PUZZLE" id="X_26_THE_JUNIOR_CLERKS_PUZZLE"></a><a href="#X_26_THE_JUNIOR_CLERKS_PUZZLEa"><b>26.—THE JUNIOR CLERK'S PUZZLE.</b></a></p> + +<p>Two youths, bearing the pleasant names of Moggs and Snoggs, were +employed as junior clerks by a merchant in Mincing Lane. They were +both engaged at the same salary—that is, commencing at the rate of +£50 a year, payable half-yearly. Moggs had a yearly rise of £10, and +Snoggs was offered the same, only he asked, for reasons that do not +concern our puzzle, that he might take his rise at £2, 10<i>s</i>. +half-yearly, to which his employer (not, perhaps, unnaturally!) had no +objection.</p> + +<p>Now we come to the real point of the puzzle. Moggs put regularly into +the Post Office Savings Bank a certain proportion of his salary, while +Snoggs saved twice as great a proportion of his, and at the end of +five years they had together saved £268, 15<i>s</i>. How much had each saved? +The question of interest can be ignored.</p> + +<hr style="width: 30%;" /> +<p><a name="X_27_GIVING_CHANGE" id="X_27_GIVING_CHANGE"></a><a href="#X_27_GIVING_CHANGEa"><b>27.—GIVING CHANGE.</b></a></p> + +<p>Every one is familiar with the difficulties that frequently arise over +the giving of change, and how the assistance of a third person with a +few coins in his pocket will sometimes help us to set the matter +right. Here is an example. An Englishman went into a shop in New York +and bought goods at a cost of thirty-four cents. The only money he had +was a dollar, a three-cent piece, and a two-cent piece. The tradesman +had only a half-dollar and a quarter-dollar. But another customer +happened to be present, and when asked to help produced two dimes, a +five-cent piece, a two-cent piece, and a one-cent piece. How did the +tradesman manage to give change? For the benefit of those readers who +are not familiar with the American coinage, it is only necessary to +say that a dollar is a hundred cents and a dime ten cents. A puzzle of +this kind should rarely cause any difficulty if attacked in a proper +manner.</p> + +<hr style="width: 30%;" /> +<p><a name="X_28_DEFECTIVE_OBSERVATION" id="X_28_DEFECTIVE_OBSERVATION"></a><a href="#X_28_DEFECTIVE_OBSERVATIONa"><b>28.—DEFECTIVE OBSERVATION.</b></a></p> + +<p>Our observation of little things is frequently defective, and our +memories very liable to lapse. A certain judge recently remarked in a +case that he had no recollection whatever of putting the wedding-ring +on his wife's finger. Can you correctly answer these questions without +having the coins in sight? On which side of a penny is the date given? +Some people are so unobservant that, although they are handling the +coin nearly every day of their lives, they are at a loss to answer +this simple question. If I lay a penny flat on the table, how many +other pennies can I place around it, every one also lying flat on the +table, so that they all touch the first one? The geometrician will, of +course, give the answer at once, and not need to make any experiment. +<span class='pagenum'>Pg 5<a name="Page_5" id="Page_5"></a></span>He will also know that, since all circles are similar, the same +answer will necessarily apply to any coin. The next question is a most +interesting one to ask a company, each person writing down his answer +on a slip of paper, so that no one shall be helped by the answers of +others. What is the greatest number of three-penny-pieces that may be +laid flat on the surface of a half-crown, so that no piece lies on +another or overlaps the surface of the half-crown? It is amazing what +a variety of different answers one gets to this question. Very few +people will be found to give the correct number. Of course the answer +must be given without looking at the coins.</p> + +<hr style="width: 30%;" /> +<p><a name="X_29_THE_BROKEN_COINS" id="X_29_THE_BROKEN_COINS"></a><a href="#X_29_THE_BROKEN_COINSa"><b>29.—THE BROKEN COINS.</b></a></p> + +<p>A man had three coins—a sovereign, a shilling, and a penny—and he +found that exactly the same fraction of each coin had been broken +away. Now, assuming that the original intrinsic value of these coins +was the same as their nominal value—that is, that the sovereign was +worth a pound, the shilling worth a shilling, and the penny worth a +penny—what proportion of each coin has been lost if the value of the +three remaining fragments is exactly one pound?</p> + +<hr style="width: 30%;" /> +<p><a name="X_30_TWO_QUESTIONS_IN_PROBABILITIES" id="X_30_TWO_QUESTIONS_IN_PROBABILITIES"></a><a href="#X_30_TWO_QUESTIONS_IN_PROBABILITIESa"><b>30.—TWO QUESTIONS IN PROBABILITIES.</b></a></p> + +<p>There is perhaps no class of puzzle over which people so frequently +blunder as that which involves what is called the theory of +probabilities. I will give two simple examples of the sort of puzzle I +mean. They are really quite easy, and yet many persons are tripped up +by them. A friend recently produced five pennies and said to me: "In +throwing these five pennies at the same time, what are the chances +that at least four of the coins will turn up either all heads or all +tails?" His own solution was quite wrong, but the correct answer ought +not to be hard to discover. Another person got a wrong answer to the +following little puzzle which I heard him propound: "A man placed +three sovereigns and one shilling in a bag. How much should be paid +for permission to draw one coin from it?" It is, of course, understood +that you are as likely to draw any one of the four coins as another.</p> + +<hr style="width: 30%;" /> +<p><a name="X_31_DOMESTIC_ECONOMY" id="X_31_DOMESTIC_ECONOMY"></a><a href="#X_31_DOMESTIC_ECONOMYa"><b>31.—DOMESTIC ECONOMY.</b></a></p> + +<p>Young Mrs. Perkins, of Putney, writes to me as follows: "I should be +very glad if you could give me the answer to a little sum that has +been worrying me a good deal lately. Here it is: We have only been +married a short time, and now, at the end of two years from the time +when we set up housekeeping, my husband tells me that he finds we have +spent a third of his yearly income in rent, rates, and taxes, one-half +in domestic expenses, and one-ninth in other ways. He has a balance of +£190 remaining in the bank. I know this last, because he accidentally +left out his pass-book the other day, and I peeped into it. Don't you +think that a husband ought to give his wife his entire confidence in +his money matters? Well, I do; and—will you believe it?—he has never +told me what his income really is, and I want, very naturally, to find +out. Can you tell me what it is from the figures I have given you?"</p> + +<p>Yes; the answer can certainly be given from the figures contained in +Mrs. Perkins's letter. And my readers, if not warned, will be +practically unanimous in declaring the income to be—something +absurdly in excess of the correct answer!</p> + +<hr style="width: 30%;" /> +<p><a name="X_32_THE_EXCURSION_TICKET_PUZZLE" id="X_32_THE_EXCURSION_TICKET_PUZZLE"></a><a href="#X_32_THE_EXCURSION_TICKET_PUZZLEa"><b>32.—THE EXCURSION TICKET PUZZLE.</b></a></p> + +<p>When the big flaming placards were exhibited at the little provincial +railway station, announcing that the Great —— Company would run +cheap excursion trains to London for the Christmas holidays, the +inhabitants of Mudley-cum-Turmits were in quite a flutter of +excitement. Half an hour before the train came in the little booking +office was crowded with country passengers, all bent on visiting their +friends in the great Metropolis. The booking clerk was unaccustomed to +dealing with crowds of such a dimension, and he told me afterwards, +while wiping his manly brow, that what caused him so much trouble was +the fact that these rustics paid their fares in such a lot of small +money.</p> + +<p>He said that he had enough farthings to supply a West End draper with +change for a week, and a sufficient number of threepenny pieces for +the congregations of three parish churches. "That excursion fare," +said he, "is nineteen shillings and ninepence, and I should like to +know in just how many different ways it is possible for such an amount +to be paid in the current coin of this realm."</p> + +<p>Here, then, is a puzzle: In how many different ways may nineteen +shillings and ninepence be paid in our current coin? Remember that the +fourpenny-piece is not now current.</p> + +<hr style="width: 30%;" /> +<p><a name="X_33_A_PUZZLE_IN_REVERSALS" id="X_33_A_PUZZLE_IN_REVERSALS"></a><a href="#X_33_A_PUZZLE_IN_REVERSALSa"><b>33.—A PUZZLE IN REVERSALS.</b></a></p> + +<p>Most people know that if you take any sum of money in pounds, +shillings, and pence, in which the number of pounds (less than £12) +exceeds that of the pence, reverse it (calling the pounds pence and +the pence pounds), find the difference, then reverse and add this +difference, the result is always £12, 18<i>s</i>. 11<i>d</i>. But if we omit the +condition, "less than £12," and allow nought to represent shillings or +pence—(1) What is the lowest amount to which the rule will not apply? +(2) What is the highest amount to which it will apply? Of course, when +reversing such a sum as £14, 15<i>s</i>. 3<i>d</i>. it may be written £3, 16<i>s</i>. 2<i>d</i>., +which is the same as £3, 15<i>s</i>. 14<i>d</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_34_THE_GROCER_AND_DRAPER" id="X_34_THE_GROCER_AND_DRAPER"></a><a href="#X_34_THE_GROCER_AND_DRAPERa"><b>34.—THE GROCER AND DRAPER.</b></a></p> + +<p>A country "grocer and draper" had two rival assistants, who prided +themselves on their rapidity in serving customers. The young man on +the grocery side could weigh up two one-pound parcels of sugar per +minute, while the drapery assistant could cut three one-yard lengths +of cloth in the same time. Their employer, one slack day, set them a +race, giving <span class='pagenum'>Pg 6<a name="Page_6" id="Page_6"></a></span>the grocer a barrel of sugar and telling him to weigh up +forty-eight one-pound parcels of sugar While the draper divided a roll +of forty-eight yards of cloth into yard pieces. The two men were +interrupted together by customers for nine minutes, but the draper was +disturbed seventeen times as long as the grocer. What was the result +of the race?</p> +<hr style="width: 30%;" /> +<p><a name="X_35_JUDKINSS_CATTLE" id="X_35_JUDKINSS_CATTLE"></a><a href="#X_35_JUDKINSS_CATTLEa"><b>35.—JUDKINS'S CATTLE.</b></a></p> + +<p>Hiram B. Judkins, a cattle-dealer of Texas, had five droves of +animals, consisting of oxen, pigs, and sheep, with the same number of +animals in each drove. One morning he sold all that he had to eight +dealers. Each dealer bought the same number of animals, paying +seventeen dollars for each ox, four dollars for each pig, and two +dollars for each sheep; and Hiram received in all three hundred and +one dollars. What is the greatest number of animals he could have had? +And how many would there be of each kind?</p> +<hr style="width: 30%;" /> +<p><a name="X_36_BUYING_APPLES" id="X_36_BUYING_APPLES"></a><a href="#X_36_BUYING_APPLESa"><b>36.—BUYING APPLES.</b></a></p> + +<p>As the purchase of apples in small quantities has always presented +considerable difficulties, I think it well to offer a few remarks on +this subject. We all know the story of the smart boy who, on being +told by the old woman that she was selling her apples at four for +threepence, said: "Let me see! Four for threepence; that's three for +twopence, two for a penny, one for nothing—I'll take <i>one</i>!"</p> + +<p>There are similar cases of perplexity. For example, a boy once picked +up a penny apple from a stall, but when he learnt that the woman's +pears were the same price he exchanged it, and was about to walk off. +"Stop!" said the woman. "You haven't paid me for the pear!" "No," said +the boy, "of course not. I gave you the apple for it." "But you didn't +pay for the apple!" "Bless the woman! You don't expect me to pay for +the apple and the pear too!" And before the poor creature could get +out of the tangle the boy had disappeared.</p> + +<p>Then, again, we have the case of the man who gave a boy sixpence and +promised to repeat the gift as soon as the youngster had made it into +ninepence. Five minutes later the boy returned. "I have made it into +ninepence," he said, at the same time handing his benefactor +threepence. "How do you make that out?" he was asked. "I bought +threepennyworth of apples." "But that does not make it into +ninepence!" "I should rather think it did," was the boy's reply. "The +apple woman has threepence, hasn't she? Very well, I have +threepennyworth of apples, and I have just given you the other +threepence. What's that but ninepence?"</p> + +<p>I cite these cases just to show that the small boy really stands in +need of a little instruction in the art of buying apples. So I will +give a simple poser dealing with this branch of commerce.</p> + +<p>An old woman had apples of three sizes for sale—one a penny, two a +penny, and three a penny. Of course two of the second size and three +of the third size were respectively equal to one apple of the largest +size. Now, a gentleman who had an equal number of boys and girls gave +his children sevenpence to be spent amongst them all on these apples. +The puzzle is to give each child an equal distribution of apples. How +was the sevenpence spent, and how many children were there?</p> + +<hr style="width: 30%;" /> +<p><a name="X_37_BUYING_CHESTNUTS" id="X_37_BUYING_CHESTNUTS"></a><a href="#X_37_BUYING_CHESTNUTSa"><b>37.—BUYING CHESTNUTS.</b></a></p> + +<p>Though the following little puzzle deals with the purchase of +chestnuts, it is not itself of the "chestnut" type. It is quite new. +At first sight it has certainly the appearance of being of the +"nonsense puzzle" character, but it is all right when properly +considered.</p> + +<p>A man went to a shop to buy chestnuts. He said he wanted a pennyworth, +and was given five chestnuts. "It is not enough; I ought to have a +sixth," he remarked! "But if I give you one chestnut more." the +shopman replied, "you will have five too many." Now, strange to say, +they were both right. How many chestnuts should the buyer receive for +half a crown?</p> + +<hr style="width: 30%;" /> +<p><a name="X_38_THE_BICYCLE_THIEF" id="X_38_THE_BICYCLE_THIEF"></a><a href="#X_38_THE_BICYCLE_THIEFa"><b>38.—THE BICYCLE THIEF.</b></a></p> + +<p>Here is a little tangle that is perpetually cropping up in various +guises. A cyclist bought a bicycle for £15 and gave in payment a +cheque for £25. The seller went to a neighbouring shopkeeper and got +him to change the cheque for him, and the cyclist, having received his +£10 change, mounted the machine and disappeared. The cheque proved to +be valueless, and the salesman was requested by his neighbour to +refund the amount he had received. To do this, he was compelled to +borrow the £25 from a friend, as the cyclist forgot to leave his +address, and could not be found. Now, as the bicycle cost the salesman +£11, how much money did he lose altogether?</p> + +<hr style="width: 30%;" /> +<p><a name="X_39_THE_COSTERMONGERS_PUZZLE" id="X_39_THE_COSTERMONGERS_PUZZLE"></a><a href="#X_39_THE_COSTERMONGERS_PUZZLEa"><b>39.—THE COSTERMONGER'S PUZZLE.</b></a></p> + +<p>"How much did yer pay for them oranges, Bill?"</p> + +<p>"I ain't a-goin' to tell yer, Jim. But I beat the old cove down +fourpence a hundred."</p> + +<p>"What good did that do yer?"</p> + +<p>"Well, it meant five more oranges on every ten shillin's-worth."</p> + +<p>Now, what price did Bill actually pay for the oranges? There is only +one rate that will fit in with his statements.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="AGE_AND_KINSHIP_PUZZLES" id="AGE_AND_KINSHIP_PUZZLES"></a><a href="#CONTENTS">AGE AND KINSHIP PUZZLES.</a></h2> + +<p class='center'> +<span style="margin-left: 0em;">"The days of our years are threescore years and ten."<br /></span> +<span style="margin-left: 8em;">—<i>Psalm</i> xc. 10.<br /></span> +</p> + +<p>For centuries it has been a favourite method of propounding +arithmetical puzzles to pose them in the form of questions as to the +age of an individual. They generally lend themselves to very easy +solution by the use of algebra, though often the difficulty lies in +stating them <span class='pagenum'>Pg 7<a name="Page_7" id="Page_7"></a></span>correctly. They may be made very complex and may demand +considerable ingenuity, but no general laws can well be laid down for +their solution. The solver must use his own sagacity. As for puzzles +in relationship or kinship, it is quite curious how bewildering many +people find these things. Even in ordinary conversation, some +statement as to relationship, which is quite clear in the mind of the +speaker, will immediately tie the brains of other people into knots. +Such expressions as "He is my uncle's son-in-law's sister" convey +absolutely nothing to some people without a detailed and laboured +explanation. In such cases the best course is to sketch a brief +genealogical table, when the eye comes immediately to the assistance +of the brain. In these days, when we have a growing lack of respect +for pedigrees, most people have got out of the habit of rapidly +drawing such tables, which is to be regretted, as they would save a +lot of time and brain racking on occasions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_40_MAMMAS_AGE" id="X_40_MAMMAS_AGE"></a><a href="#X_40_MAMMAS_AGEa"><b>40.—MAMMA'S AGE.</b></a></p> + +<p>Tommy: "How old are you, mamma?"</p> + +<p>Mamma: "Let me think, Tommy. Well, our three ages add up to exactly +seventy years."</p> + +<p>Tommy: "That's a lot, isn't it? And how old are you, papa?"</p> + +<p>Papa: "Just six times as old as you, my son."</p> + +<p>Tommy: "Shall I ever be half as old as you, papa?"</p> + +<p>Papa: "Yes, Tommy; and when that happens our three ages will add up to +exactly twice as much as to-day."</p> + +<p>Tommy: "And supposing I was born before you, papa; and supposing mamma +had forgot all about it, and hadn't been at home when I came; and +supposing——"</p> + +<p>Mamma: "Supposing, Tommy, we talk about bed. Come along, darling. +You'll have a headache."</p> + +<p>Now, if Tommy had been some years older he might have calculated the +exact ages of his parents from the information they had given him. Can +you find out the exact age of mamma?</p> + +<hr style="width: 30%;" /> +<p><a name="X_41_THEIR_AGES" id="X_41_THEIR_AGES"></a><a href="#X_41_THEIR_AGESa"><b>41.—THEIR AGES.</b></a></p> + +<p>"My husband's age," remarked a lady the other day, "is represented by +the figures of my own age reversed. He is my senior, and the +difference between our ages is one-eleventh of their sum."</p> + +<hr style="width: 30%;" /> +<p><a name="X_42_THE_FAMILY_AGES" id="X_42_THE_FAMILY_AGES"></a><a href="#X_42_THE_FAMILY_AGESa"><b>42.—THE FAMILY AGES.</b></a></p> + +<p>When the Smileys recently received a visit from the favourite uncle, +the fond parents had all the five children brought into his presence. +First came Billie and little Gertrude, and the uncle was informed that +the boy was exactly twice as old as the girl. Then Henrietta arrived, +and it was pointed out that the combined ages of herself and Gertrude +equalled twice the age of Billie. Then Charlie came running in, and +somebody remarked that now the combined ages of the two boys were +exactly twice the combined ages of the two girls. The uncle was +expressing his astonishment at these coincidences when Janet came in. +"Ah! uncle," she exclaimed, "you have actually arrived on my +twenty-first birthday!" To this Mr. Smiley added the final staggerer: +"Yes, and now the combined ages of the three girls are exactly equal +to twice the combined ages of the two boys." Can you give the age of +each child?</p> + +<hr style="width: 30%;" /> +<p><a name="X_43_MRS_TIMPKINSS_AGE" id="X_43_MRS_TIMPKINSS_AGE"></a><a href="#X_43_MRS_TIMPKINSS_AGEa"><b>43.—MRS. TIMPKINS'S AGE.</b></a></p> + +<p>Edwin: "Do you know, when the Timpkinses married eighteen years ago +Timpkins was three times as old as his wife, and to-day he is just +twice as old as she?"</p> + +<p>Angelina: "Then how old was Mrs. Timpkins on the wedding day?"</p> + +<p>Can you answer Angelina's question?</p> + +<hr style="width: 30%;" /> +<p><a name="X_44_A_CENSUS_PUZZLE" id="X_44_A_CENSUS_PUZZLE"></a><a href="#X_44_A_CENSUS_PUZZLEa"><b>44—A CENSUS PUZZLE.</b></a></p> + +<p>Mr. and Mrs. Jorkins have fifteen children, all born at intervals of +one year and a half. Miss Ada Jorkins, the eldest, had an objection to +state her age to the census man, but she admitted that she was just +seven times older than little Johnnie, the youngest of all. What was +Ada's age? Do not too hastily assume that you have solved this little +poser. You may find that you have made a bad blunder!</p> + +<hr style="width: 30%;" /> +<p><a name="X_45_MOTHER_AND_DAUGHTER" id="X_45_MOTHER_AND_DAUGHTER"></a><a href="#X_45_MOTHER_AND_DAUGHTERa"><b>45.—MOTHER AND DAUGHTER.</b></a></p> + +<p>"Mother, I wish you would give me a bicycle," said a girl of twelve +the other day.</p> + +<p>"I do not think you are old enough yet, my dear," was the reply. "When +I am only three times as old as you are you shall have one."</p> + +<p>Now, the mother's age is forty-five years. When may the young lady +expect to receive her present?</p> + +<hr style="width: 30%;" /> +<p><a name="X_46_MARY_AND_MARMADUKE" id="X_46_MARY_AND_MARMADUKE"></a><a href="#X_46_MARY_AND_MARMADUKEa"><b>46.—MARY AND MARMADUKE.</b></a></p> + +<p>Marmaduke: "Do you know, dear, that in seven years' time our combined +ages will be sixty-three years?"</p> + +<p>Mary: "Is that really so? And yet it is a fact that when you were my +present age you were twice as old as I was then. I worked it out last +night."</p> + +<p>Now, what are the ages of Mary and Marmaduke?</p> + +<hr style="width: 30%;" /> +<p><a name="X_47_ROVERS_AGE" id="X_47_ROVERS_AGE"></a><a href="#X_47_ROVERS_AGEa"><b>47—ROVER'S AGE.</b></a></p> + +<p>"Now, then, Tommy, how old is Rover?" Mildred's young man asked her +brother.</p> + +<p>"Well, five years ago," was the youngster's reply, "sister was four +times older than the dog, but now she is only three times as old."</p> + +<p>Can you tell Rover's age?</p> + +<hr style="width: 30%;" /> +<p><a name="X_48_CONCERNING_TOMMYS_AGE" id="X_48_CONCERNING_TOMMYS_AGE"></a><a href="#X_48_CONCERNING_TOMMYS_AGEa"><b>48.—CONCERNING TOMMY'S AGE.</b></a></p> + +<p>Tommy Smart was recently sent to a new school. On the first day of his +arrival the teacher asked him his age, and this was his curious reply: +"Well, you see, it is like this. At the time I was born—I forget the +year—my only sister, Ann, happened to be just one-quarter the age <span class='pagenum'>Pg 8<a name="Page_8" id="Page_8"></a></span>of +mother, and she is now one-third the age of father." "That's all very +well," said the teacher, "but what I want is not the age of your +sister Ann, but your own age." "I was just coming to that," Tommy +answered; "I am just a quarter of mother's present age, and in four +years' time I shall be a quarter the age of father. Isn't that funny?"</p> + +<p>This was all the information that the teacher could get out of Tommy +Smart. Could you have told, from these facts, what was his precise +age? It is certainly a little puzzling.</p> + +<hr style="width: 30%;" /> +<p><a name="X_49_NEXT-DOOR_NEIGHBOURS" id="X_49_NEXT-DOOR_NEIGHBOURS"></a><a href="#X_49_NEXT-DOOR_NEIGHBOURSa"><b>49.—NEXT-DOOR NEIGHBOURS.</b></a></p> + +<p>There were two families living next door to one another at Tooting +Bec—the Jupps and the Simkins. The united ages of the four Jupps +amounted to one hundred years, and the united ages of the Simkins also +amounted to the same. It was found in the case of each family that the +sum obtained by adding the squares of each of the children's ages to +the square of the mother's age equalled the square of the father's +age. In the case of the Jupps, however, Julia was one year older than +her brother Joe, whereas Sophy Simkin was two years older than her +brother Sammy. What was the age of each of the eight individuals?</p> + +<hr style="width: 30%;" /> +<p><a name="X_50_THE_BAG_OF_NUTS" id="X_50_THE_BAG_OF_NUTS"></a><a href="#X_50_THE_BAG_OF_NUTSa"><b>50.—THE BAG OF NUTS.</b></a></p> + +<p>Three boys were given a bag of nuts as a Christmas present, and it was +agreed that they should be divided in proportion to their ages, which +together amounted to 17½ years. Now the bag contained 770 nuts, and +as often as Herbert took four Robert took three, and as often as +Herbert took six Christopher took seven. The puzzle is to find out how +many nuts each had, and what were the boys' respective ages.</p> + +<hr style="width: 30%;" /> +<p><a name="X_51_HOW_OLD_WAS_MARY" id="X_51_HOW_OLD_WAS_MARY"></a><a href="#X_51_HOW_OLD_WAS_MARYa"><b>51.—HOW OLD WAS MARY?</b></a></p> + +<p>Here is a funny little age problem, by the late Sam Loyd, which has +been very popular in the United States. Can you unravel the mystery?</p> + +<p>The combined ages of Mary and Ann are forty-four years, and Mary is +twice as old as Ann was when Mary was half as old as Ann will be when +Ann is three times as old as Mary was when Mary was three times as old +as Ann. How old is Mary? That is all, but can you work it out? If not, +ask your friends to help you, and watch the shadow of bewilderment +creep over their faces as they attempt to grip the intricacies of the +question.</p> + +<hr style="width: 30%;" /> +<p><a name="X_52_QUEER_RELATIONSHIPS" id="X_52_QUEER_RELATIONSHIPS"></a><a href="#X_52_QUEER_RELATIONSHIPSa"><b>52.—QUEER RELATIONSHIPS.</b></a></p> + +<p>"Speaking of relationships," said the Parson at a certain +dinner-party, "our legislators are getting the marriage law into a +frightful tangle, Here, for example, is a puzzling case that has come +under my notice. Two brothers married two sisters. One man died and +the other man's wife also died. Then the survivors married."</p> + +<p>"The man married his deceased wife's sister under the recent Act?" put +in the Lawyer.</p> + +<p>"Exactly. And therefore, under the civil law, he is legally married +and his child is legitimate. But, you see, the man is the woman's +deceased husband's brother, and therefore, also under the civil law, +she is not married to him and her child is illegitimate."</p> + +<p>"He is married to her and she is not married to him!" said the Doctor.</p> + +<p>"Quite so. And the child is the legitimate son of his father, but the +illegitimate son of his mother."</p> + +<p>"Undoubtedly 'the law is a hass,'" the Artist exclaimed, "if I may be +permitted to say so," he added, with a bow to the Lawyer.</p> + +<p>"Certainly," was the reply. "We lawyers try our best to break in the +beast to the service of man. Our legislators are responsible for the +breed."</p> + +<p>"And this reminds me," went on the Parson, "of a man in my parish who +married the sister of his widow. This man——"</p> + +<p>"Stop a moment, sir," said the Professor. "Married the sister of his +widow? Do you marry dead men in your parish?"</p> + +<p>"No; but I will explain that later. Well, this man has a sister of his +own. Their names are Stephen Brown and Jane Brown. Last week a young +fellow turned up whom Stephen introduced to me as his nephew. +Naturally, I spoke of Jane as his aunt, but, to my astonishment, the +youth corrected me, assuring me that, though he was the nephew of +Stephen, he was not the nephew of Jane, the sister of Stephen. This +perplexed me a good deal, but it is quite correct."</p> + +<p>The Lawyer was the first to get at the heart of the mystery. What was +his solution?</p> + +<hr style="width: 30%;" /> +<p><a name="X_53_HEARD_ON_THE_TUBE_RAILWAY" id="X_53_HEARD_ON_THE_TUBE_RAILWAY"></a><a href="#X_53_HEARD_ON_THE_TUBE_RAILWAYa"><b>53.—HEARD ON THE TUBE RAILWAY.</b></a></p> + +<p>First Lady: "And was he related to you, dear?"</p> + +<p>Second Lady: "Oh, yes. You see, that gentleman's mother was my +mother's mother-in-law, but he is not on speaking terms with my papa."</p> + +<p>First Lady: "Oh, indeed!" (But you could see that she was not much +wiser.)</p> + +<p>How was the gentleman related to the Second Lady?</p> + +<hr style="width: 30%;" /> +<p><a name="X_54_A_FAMILY_PARTY" id="X_54_A_FAMILY_PARTY"></a><a href="#X_54_A_FAMILY_PARTYa"><b>54.—A FAMILY PARTY.</b></a></p> + +<p>A certain family party consisted of 1 grandfather, 1 grandmother, 2 +fathers, 2 mothers, 4 children, 3 grandchildren, 1 brother, 2 sisters, +2 sons, 2 daughters, 1 father-in-law, 1 mother-in-law, and 1 +daughter-in-law. Twenty-three people, you will say. No; there were +only seven persons present. Can you show how this might be?</p> + +<hr style="width: 30%;" /> +<p><a name="X_55_A_MIXED_PEDIGREE" id="X_55_A_MIXED_PEDIGREE"></a><a href="#X_55_A_MIXED_PEDIGREEa"><b>55.—A MIXED PEDIGREE.</b></a></p> + +<p>Joseph Bloggs: "I can't follow it, my dear boy. It makes me dizzy!"</p> + +<p>John Snoggs: "It's very simple. Listen again! You happen to be my +father's brother-in-law, my brother's father-in-law, and also my +father-in-law's brother. You see, my father was——"</p> + +<p><span class='pagenum'>Pg 9<a name="Page_9" id="Page_9"></a></span>But Mr. Bloggs refused to hear any more. Can the reader show how this +extraordinary triple relationship might have come about?</p> + +<hr style="width: 30%;" /> +<p><a name="X_56_WILSONS_POSER" id="X_56_WILSONS_POSER"></a><a href="#X_56_WILSONS_POSERa"><b>56.—WILSON'S POSER.</b></a></p> + +<p>"Speaking of perplexities——" said Mr. Wilson, throwing down a +magazine on the table in the commercial room of the Railway Hotel.</p> + +<p>"Who was speaking of perplexities?" inquired Mr. Stubbs.</p> + +<p>"Well, then, reading about them, if you want to be exact—it just +occurred to me that perhaps you three men may be interested in a +little matter connected with myself."</p> + +<p>It was Christmas Eve, and the four commercial travellers were spending +the holiday at Grassminster. Probably each suspected that the others +had no homes, and perhaps each was conscious of the fact that he was +in that predicament himself. In any case they seemed to be perfectly +comfortable, and as they drew round the cheerful fire the conversation +became general.</p> + +<p>"What is the difficulty?" asked Mr. Packhurst.</p> + +<p>"There's no difficulty in the matter, when you rightly understand it. +It is like this. A man named Parker had a flying-machine that would +carry two. He was a venturesome sort of chap—reckless, I should call +him—and he had some bother in finding a man willing to risk his life +in making an ascent with him. However, an uncle of mine thought he +would chance it, and one fine morning he took his seat in the machine +and she started off well. When they were up about a thousand feet, my +nephew suddenly——"</p> + +<p>"Here, stop, Wilson! What was your nephew doing there? You said your +uncle," interrupted Mr. Stubbs.</p> + +<p>"Did I? Well, it does not matter. My nephew suddenly turned to Parker +and said that the engine wasn't running well, so Parker called out to +my uncle——"</p> + +<p>"Look here," broke in Mr. Waterson, "we are getting mixed. Was it your +uncle or your nephew? Let's have it one way or the other."</p> + +<p>"What I said is quite right. Parker called out to my uncle to do +something or other, when my nephew——"</p> + +<p>"There you are again, Wilson," cried Mr. Stubbs; "once for all, are we +to understand that both your uncle and your nephew were on the +machine?"</p> + +<p>"Certainly. I thought I made that clear. Where was I? Well, my nephew +shouted back to Parker——"</p> + +<p>"Phew! I'm sorry to interrupt you again, Wilson, but we can't get on +like this. Is it true that the machine would only carry two?"</p> + +<p>"Of course. I said at the start that it only carried two."</p> + +<p>"Then what in the name of aerostation do you mean by saying that there +were three persons on board?" shouted Mr. Stubbs.</p> + +<p>"Who said there were three?"</p> + +<p>"You have told us that Parker, your uncle, and your nephew went up on +this blessed flying-machine."</p> + +<p>"That's right."</p> + +<p>"And the thing would only carry two!"</p> + +<p>"Right again."</p> + +<p>"Wilson, I have known you for some time as a truthful man and a +temperate man," said Mr. Stubbs, solemnly. "But I am afraid since you +took up that new line of goods you have overworked yourself."</p> + +<p>"Half a minute, Stubbs," interposed Mr. Waterson. "I see clearly where +we all slipped a cog. Of course, Wilson, you meant us to understand +that Parker is either your uncle or your nephew. Now we shall be all +right if you will just tell us whether Parker is your uncle or +nephew."</p> + +<p>"He is no relation to me whatever."</p> + +<p>The three men sighed and looked anxiously at one another. Mr. Stubbs +got up from his chair to reach the matches, Mr. Packhurst proceeded to +wind up his watch, and Mr. Waterson took up the poker to attend to the +fire. It was an awkward moment, for at the season of goodwill nobody +wished to tell Mr. Wilson exactly what was in his mind.</p> + +<p>"It's curious," said Mr. Wilson, very deliberately, "and it's rather +sad, how thick-headed some people are. You don't seem to grip the +facts. It never seems to have occurred to either of you that my uncle +and my nephew are one and the same man."</p> + +<p>"What!" exclaimed all three together.</p> + +<p>"Yes; David George Linklater is my uncle, and he is also my nephew. +Consequently, I am both his uncle and nephew. Queer, isn't it? I'll +explain how it comes about."</p> + +<p>Mr. Wilson put the case so very simply that the three men saw how it +might happen without any marriage within the prohibited degrees. +Perhaps the reader can work it out for himself.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="CLOCK_PUZZLES" id="CLOCK_PUZZLES"></a><a href="#CONTENTS">CLOCK PUZZLES.</a></h2> + +<p class='center'> +<span style="margin-left: 0em;">"Look at the clock!"</span><br /> +<span style="margin-left: 8em;"><i>Ingoldsby Legends</i>.</span><br /> +</p> + + +<p>In considering a few puzzles concerning clocks and watches, and the +times recorded by their hands under given conditions, it is well that +a particular convention should always be kept in mind. It is +frequently the case that a solution requires the assumption that the +hands can actually record a time involving a minute fraction of a +second. Such a time, of course, cannot be really indicated. Is the +puzzle, therefore, impossible of solution? The conclusion deduced from +a logical syllogism depends for its truth on the two premises assumed, +and it is the same in mathematics. Certain things are antecedently +assumed, and the answer depends entirely on the truth of those +assumptions.</p> + +<p>"If two horses," says Lagrange, "can pull a load of a certain weight, +it is natural to suppose that four horses could pull a load of double +that weight, six horses a load of three times that weight. Yet, +strictly speaking, such is not the <span class='pagenum'>Pg 10<a name="Page_10" id="Page_10"></a></span>case. For the inference is based +on the assumption that the four horses pull alike in amount and +direction, which in practice can scarcely ever be the case. It so +happens that we are frequently led in our reckonings to results which +diverge widely from reality. But the fault is not the fault of +mathematics; for mathematics always gives back to us exactly what we +have put into it. The ratio was constant according to that +supposition. The result is founded upon that supposition. If the +supposition is false the result is necessarily false."</p> + +<p>If one man can reap a field in six days, we say two men will reap it +in three days, and three men will do the work in two days. We here +assume, as in the case of Lagrange's horses, that all the men are +exactly equally capable of work. But we assume even more than this. +For when three men get together they may waste time in gossip or play; +or, on the other hand, a spirit of rivalry may spur them on to greater +diligence. We may assume any conditions we like in a problem, provided +they be clearly expressed and understood, and the answer will be in +accordance with those conditions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_57_WHAT_WAS_THE_TIME" id="X_57_WHAT_WAS_THE_TIME"></a><a href="#X_57_WHAT_WAS_THE_TIMEa"><b>57.—WHAT WAS THE TIME?</b></a></p> + +<p>"I say, Rackbrane, what is the time?" an acquaintance asked our friend +the professor the other day. The answer was certainly curious.</p> + +<p>"If you add one quarter of the time from noon till now to half the +time from now till noon to-morrow, you will get the time exactly."</p> + +<p>What was the time of day when the professor spoke?</p> + +<hr style="width: 30%;" /> +<p><a name="X_58_A_TIME_PUZZLE" id="X_58_A_TIME_PUZZLE"></a><a href="#X_58_A_TIME_PUZZLEa"><b>58.—A TIME PUZZLE.</b></a></p> + +<p>How many minutes is it until six o'clock if fifty minutes ago it was +four times as many minutes past three o'clock?</p> + +<hr style="width: 30%;" /> +<p><a name="X_59_A_PUZZLING_WATCH" id="X_59_A_PUZZLING_WATCH"></a><a href="#X_59_A_PUZZLING_WATCHa"><b>59.—A PUZZLING WATCH.</b></a></p> + +<p>A friend pulled out his watch and said, "This watch of mine does not +keep perfect time; I must have it seen to. I have noticed that the +minute hand and the hour hand are exactly together every sixty-five +minutes." Does that watch gain or lose, and how much per hour?</p> + +<hr style="width: 30%;" /> +<p><a name="X_60_THE_WAPSHAWS_WHARF_MYSTERY" id="X_60_THE_WAPSHAWS_WHARF_MYSTERY"></a><a href="#X_60_THE_WAPSHAWS_WHARF_MYSTERYa"><b>60.—THE WAPSHAW'S WHARF MYSTERY.</b></a></p> + +<p>There was a great commotion in Lower Thames Street on the morning of +January 12, 1887. When the early members of the staff arrived at +Wapshaw's Wharf they found that the safe had been broken open, a +considerable sum of money removed, and the offices left in great +disorder. The night watchman was nowhere to be found, but nobody who +had been acquainted with him for one moment suspected him to be guilty +of the robbery. In this belief the proprietors were confirmed when, +later in the day, they were informed that the poor fellow's body had +been picked up by the River Police. Certain marks of violence pointed +to the fact that he had been brutally attacked and thrown into the +river. A watch found in his pocket had stopped, as is invariably the +case in such circumstances, and this was a valuable clue to the time +of the outrage. But a very stupid officer (and we invariably find one +or two stupid individuals in the most intelligent bodies of men) had +actually amused himself by turning the hands round and round, trying +to set the watch going again. After he had been severely reprimanded +for this serious indiscretion, he was asked whether he could remember +the time that was indicated by the watch when found. He replied that +he could not, but he recollected that the hour hand and minute hand +were exactly together, one above the other, and the second hand had +just passed the forty-ninth second. More than this he could not +remember.</p> + +<p>What was the exact time at which the watchman's watch stopped? The +watch is, of course, assumed to have been an accurate one.</p> + +<hr style="width: 30%;" /> +<p><a name="X_61_CHANGING_PLACES" id="X_61_CHANGING_PLACES"></a><a href="#X_61_CHANGING_PLACESa"><b>61.—CHANGING PLACES.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q061.png" width="400" height="397" alt="" title="" /> +</div> + +<p>The above clock face indicates a little before 42 minutes past 4. The +hands will again point at exactly the same spots a little after 23 +minutes past 8. In fact, the hands will have changed places. How many +times do the hands of a clock change places between three o'clock p.m. +and midnight? And out of all the pairs of times indicated by these +changes, what is the exact time when the minute hand will be nearest +to the point IX?</p> + +<hr style="width: 30%;" /> +<p><a name="X_62_THE_CLUB_CLOCK" id="X_62_THE_CLUB_CLOCK"></a><a href="#X_62_THE_CLUB_CLOCKa"><b>62.—THE CLUB CLOCK.</b></a></p> + +<p>One of the big clocks in the Cogitators' Club was found the other +night to have stopped just when, as will be seen in the illustration, +the second hand was exactly midway between the other two hands. One of +the members proposed to some of his friends that they should tell him +the exact time when (if the clock had not <span class='pagenum'>Pg 11<a name="Page_11" id="Page_11"></a></span>stopped) the second hand +would next again have been midway between the minute hand and the hour +hand. Can you find the correct time that it would happen?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q062.png" width="400" height="375" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_63_THE_STOP-WATCH" id="X_63_THE_STOP-WATCH"></a><a href="#X_63_THE_STOP-WATCHa"><b>63.—THE STOP-WATCH.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q063.png" width="400" height="532" alt="" title="" /> +</div> + +<p>We have here a stop-watch with three hands. The second hand, which +travels once round the face in a minute, is the one with the little +ring at its end near the centre. Our dial indicates the exact time +when its owner stopped the watch. You will notice that the three hands +are nearly equidistant. The hour and minute hands point to spots that +are exactly a third of the circumference apart, but the second hand is +a little too advanced. An exact equidistance for the three hands is +not possible. Now, we want to know what the time will be when the +three hands are next at exactly the same distances as shown from one +another. Can you state the time?</p> + +<hr style="width: 30%;" /> +<p><a name="X_64_THE_THREE_CLOCKS" id="X_64_THE_THREE_CLOCKS"></a><a href="#X_64_THE_THREE_CLOCKSa"><b>64.—THE THREE CLOCKS.</b></a></p> + +<p>On Friday, April 1, 1898, three new clocks were all set going +precisely at the same time—twelve noon. At noon on the following day +it was found that clock A had kept perfect time, that clock B had +gained exactly one minute, and that clock C had lost exactly one +minute. Now, supposing that the clocks B and C had not been regulated, +but all three allowed to go on as they had begun, and that they +maintained the same rates of progress without stopping, on what date +and at what time of day would all three pairs of hands again point at +the same moment at twelve o'clock?</p> + +<hr style="width: 30%;" /> +<p><a name="X_65_THE_RAILWAY_STATION_CLOCK" id="X_65_THE_RAILWAY_STATION_CLOCK"></a><a href="#X_65_THE_RAILWAY_STATION_CLOCKa"><b>65.—THE RAILWAY STATION CLOCK.</b></a></p> + +<p>A clock hangs on the wall of a railway station, 71 ft. 9 in. long and +10 ft. 4 in. high. Those are the dimensions of the wall, not of the +clock! While waiting for a train we noticed that the hands of the +clock were pointing in opposite directions, and were parallel to one +of the diagonals of the wall. What was the exact time?</p> + +<hr style="width: 30%;" /> +<p><a name="X_66_THE_VILLAGE_SIMPLETON" id="X_66_THE_VILLAGE_SIMPLETON"></a><a href="#X_66_THE_VILLAGE_SIMPLETONa"><b>66.—THE VILLAGE SIMPLETON.</b></a></p> + +<p>A facetious individual who was taking a long walk in the country came +upon a yokel sitting on a stile. As the gentleman was not quite sure +of his road, he thought he would make inquiries of the local +inhabitant; but at the first glance he jumped too hastily to the +conclusion that he had dropped on the village idiot. He therefore +decided to test the fellow's intelligence by first putting to him the +simplest question he could think of, which was, "What day of the week +is this, my good man?" The following is the smart answer that he +received:—</p> + +<p>"When the day after to-morrow is yesterday, to-day will be as far from +Sunday as to-day was from Sunday when the day before yesterday was +to-morrow."</p> + +<p>Can the reader say what day of the week it was? It is pretty evident +that the countryman was not such a fool as he looked. The gentleman +went on his road a puzzled but a wiser man.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="LOCOMOTION_AND_SPEED_PUZZLES" id="LOCOMOTION_AND_SPEED_PUZZLES"></a><a href="#CONTENTS">LOCOMOTION AND SPEED PUZZLES.</a></h2> + +<p class='center'>"The race is not to the swift."—<i>Ecclesiastes</i> ix. II.</p> + +<hr style="width: 30%;" /> +<p><a name="X_67_AVERAGE_SPEED" id="X_67_AVERAGE_SPEED"></a><a href="#X_67_AVERAGE_SPEEDa"><b>67.—AVERAGE SPEED.</b></a></p> + +<p>In a recent motor ride it was found that we had gone at the rate of +ten miles an hour, but we did the return journey over the same route, +owing to the roads being more clear of traffic, at fifteen miles an +hour. What was our average speed? Do not be too hasty in your answer +to this simple little question, or it is pretty certain that you will +be wrong.</p> + +<hr style="width: 30%;" /> +<p><a name="X_68_THE_TWO_TRAINS" id="X_68_THE_TWO_TRAINS"></a><a href="#X_68_THE_TWO_TRAINSa"><b>68.—THE TWO TRAINS.</b></a></p> + +<p>I put this little question to a stationmaster, and his correct answer +was so prompt that I am <span class='pagenum'>Pg 12<a name="Page_12" id="Page_12"></a></span>convinced there is no necessity to seek +talented railway officials in America or elsewhere.</p> + +<p>Two trains start at the same time, one from London to Liverpool, the +other from Liverpool to London. If they arrive at their destinations +one hour and four hours respectively after passing one another, how +much faster is one train running than the other?</p> + +<hr style="width: 30%;" /> +<p><a name="X_69_THE_THREE_VILLAGES" id="X_69_THE_THREE_VILLAGES"></a><a href="#X_69_THE_THREE_VILLAGESa"><b>69.—THE THREE VILLAGES.</b></a></p> + +<p>I set out the other day to ride in a motor-car from Acrefield to +Butterford, but by mistake I took the road going <i>via</i> Cheesebury, +which is nearer Acrefield than Butterford, and is twelve miles to the +left of the direct road I should have travelled. After arriving at +Butterford I found that I had gone thirty-five miles. What are the +three distances between these villages, each being a whole number of +miles? I may mention that the three roads are quite straight.</p> + +<hr style="width: 30%;" /> +<p><a name="X_70_DRAWING_HER_PENSION" id="X_70_DRAWING_HER_PENSION"></a><a href="#X_70_DRAWING_HER_PENSIONa"><b>70.—DRAWING HER PENSION.</b></a></p> + +<p>"Speaking of odd figures," said a gentleman who occupies some post in +a Government office, "one of the queerest characters I know is an old +lame widow who climbs up a hill every week to draw her pension at the +village post office. She crawls up at the rate of a mile and a half an +hour and comes down at the rate of four and a half miles an hour, so +that it takes her just six hours to make the double journey. Can any +of you tell me how far it is from the bottom of the hill to the top?"</p> + + +<hr style="width: 30%;" /> +<p><a name="X_71_SIR_EDWYN_DE_TUDOR" id="X_71_SIR_EDWYN_DE_TUDOR"></a><a href="#X_71_SIR_EDWYN_DE_TUDORa"><b>71.—SIR EDWYN DE TUDOR.</b></a></p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/q071.png" width="500" height="432" alt="" title="" /> +</div> + +<p>In the illustration we have a sketch of Sir Edwyn de Tudor going to +rescue his lady-love, the fair Isabella, who was held a captive by a +neighbouring wicked baron. Sir Edwyn calculated that if he rode +fifteen miles an hour he would arrive at the castle an hour too soon, +while if he rode ten miles an hour he would get there just an hour too +late. Now, it was of the first importance that he should arrive at the +exact time appointed, in order that the rescue that he had planned +should be a success, and the time of the tryst was five o'clock, when +the captive lady would be taking her afternoon tea. The puzzle is to +discover exactly how far Sir Edwyn de Tudor had to ride.</p> + +<hr style="width: 30%;" /> +<p><a name="X_72_THE_HYDROPLANE_QUESTION" id="X_72_THE_HYDROPLANE_QUESTION"></a><a href="#X_72_THE_HYDROPLANE_QUESTIONa"><b>72.—THE HYDROPLANE QUESTION.</b></a></p> + +<p>The inhabitants of Slocomb-on-Sea were greatly excited over the visit +of a certain flying man. All the town turned out to see the flight of +the wonderful hydroplane, and, of course, Dobson and his family were +there. Master Tommy was in good form, and informed his father that +Englishmen made better airmen than Scotsmen <span class='pagenum'>Pg 13<a name="Page_13" id="Page_13"></a></span>and Irishmen because they +are not so heavy. "How do you make that out?" asked Mr. Dobson. "Well, +you see," Tommy replied, "it is true that in Ireland there are men of +Cork and in Scotland men of Ayr, which is better still, but in England +there are lightermen." Unfortunately it had to be explained to Mrs. +Dobson, and this took the edge off the thing. The hydroplane flight +was from Slocomb to the neighbouring watering-place Poodleville—five +miles distant. But there was a strong wind, which so helped the airman +that he made the outward journey in the short time of ten minutes, +though it took him an hour to get back to the starting point at +Slocomb, with the wind dead against him. Now, how long would the ten +miles have taken him if there had been a perfect calm? Of course, the +hydroplane's engine worked uniformly throughout.</p> + +<hr style="width: 30%;" /> +<p><a name="X_73_DONKEY_RIDING" id="X_73_DONKEY_RIDING"></a><a href="#X_73_DONKEY_RIDINGa"><b>73.—DONKEY RIDING.</b></a></p> + +<p>During a visit to the seaside Tommy and Evangeline insisted on having +a donkey race over the mile course on the sands. Mr. Dobson and some +of his friends whom he had met on the beach acted as judges, but, as +the donkeys were familiar acquaintances and declined to part company +the whole way, a dead heat was unavoidable. However, the judges, being +stationed at different points on the course, which was marked off in +quarter-miles, noted the following results:—The first three-quarters +were run in six and three-quarter minutes, the first half-mile took +the same time as the second half, and the third quarter was run in +exactly the same time as the last quarter. From these results Mr. +Dobson amused himself in discovering just how long it took those two +donkeys to run the whole mile. Can you give the answer?</p> + +<hr style="width: 30%;" /> +<p><a name="X_74_THE_BASKET_OF_POTATOES" id="X_74_THE_BASKET_OF_POTATOES"></a><a href="#X_74_THE_BASKET_OF_POTATOESa"><b>74.—THE BASKET OF POTATOES.</b></a></p> + +<p>A man had a basket containing fifty potatoes. He proposed to his son, +as a little recreation, that he should place these potatoes on the +ground in a straight line. The distance between the first and second +potatoes was to be one yard, between the second and third three yards, +between the third and fourth five yards, between the fourth and fifth +seven yards, and so on—an increase of two yards for every successive +potato laid down. Then the boy was to pick them up and put them in the +basket one at a time, the basket being placed beside the first potato. +How far would the boy have to travel to accomplish the feat of picking +them all up? We will not consider the journey involved in placing the +potatoes, so that he starts from the basket with them all laid out.</p> + +<hr style="width: 30%;" /> +<p><a name="X_75_THE_PASSENGERS_FARE" id="X_75_THE_PASSENGERS_FARE"></a><a href="#X_75_THE_PASSENGERS_FAREa"><b>75.—THE PASSENGER'S FARE.</b></a></p> + +<p>At first sight you would hardly think there was matter for dispute in +the question involved in the following little incident, yet it took +the two persons concerned some little time to come to an agreement. +Mr. Smithers hired a motor-car to take him from Addleford to +Clinkerville and back again for £3. At Bakenham, just midway, he +picked up an acquaintance, Mr. Tompkins, and agreed to take him on to +Clinkerville and bring him back to Bakenham on the return journey. How +much should he have charged the passenger? That is the question. What +was a reasonable fare for Mr. Tompkins?</p> + + + +<hr style="width: 65%;" /> +<h2><a name="DIGITAL_PUZZLES" id="DIGITAL_PUZZLES"></a><a href="#CONTENTS">DIGITAL PUZZLES.</a></h2> + +<p class='center'> +<span style="margin-left: 0em;">"Nine worthies were they called."<br /></span> +<span style="margin-left: 8em;">DRYDEN: <i>The Flower and the Leaf.</i><br /></span> +</p> + +<p>I give these puzzles, dealing with the nine digits, a class to +themselves, because I have always thought that they deserve more +consideration than they usually receive. Beyond the mere trick of +"casting out nines," very little seems to be generally known of the +laws involved in these problems, and yet an acquaintance with the +properties of the digits often supplies, among other uses, a certain +number of arithmetical checks that are of real value in the saving of +labour. Let me give just one example—the first that occurs to me.</p> + +<p>If the reader were required to determine whether or not +15,763,530,163,289 is a square number, how would he proceed? If the +number had ended with a 2, 3, 7, or 8 in the digits place, of course +he would know that it could not be a square, but there is nothing in +its apparent form to prevent its being one. I suspect that in such a +case he would set to work, with a sigh or a groan, at the laborious +task of extracting the square root. Yet if he had given a little +attention to the study of the digital properties of numbers, he would +settle the question in this simple way. The sum of the digits is 59, +the sum of which is 14, the sum of which is 5 (which I call the +"digital root"), and therefore I know that the number cannot be a +square, and for this reason. The digital root of successive square +numbers from 1 upwards is always 1, 4, 7, or 9, and can never be +anything else. In fact, the series, 1, 4, 9, 7, 7, 9, 4, 1, 9, is +repeated into infinity. The analogous series for triangular numbers is +1, 3, 6, 1, 6, 3, 1, 9, 9. So here we have a similar negative check, +for a number cannot be triangular (that is, (n²+n)/2) if its digital +root be 2, 4, 5, 7, or 8.</p> + +<hr style="width: 30%;" /> +<p><a name="X_76_THE_BARREL_OF_BEER" id="X_76_THE_BARREL_OF_BEER"></a><a href="#X_76_THE_BARREL_OF_BEERa"><b>76.—THE BARREL OF BEER.</b></a></p> + +<p>A man bought an odd lot of wine in barrels and one barrel containing +beer. These are shown in the illustration, marked with the number of +gallons that each barrel contained. He sold a quantity of the wine to +one man and twice the quantity to another, but kept the beer to +himself. The puzzle is to point out which barrel contains beer. Can +you say which one it is? Of course, the man sold the barrels just as +he <span class='pagenum'>Pg 14<a name="Page_14" id="Page_14"></a></span>bought them, without manipulating in any way the contents.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q076.png" width="400" height="317" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_77_DIGITS_AND_SQUARES" id="X_77_DIGITS_AND_SQUARES"></a><a href="#X_77_DIGITS_AND_SQUARESa"><b>77.—DIGITS AND SQUARES.</b></a></p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/q077.png" width="300" height="268" alt="" title="" /> +</div> + +<p>It will be seen in the diagram that we have so arranged the nine +digits in a square that the number in the second row is twice that in +the first row, and the number in the bottom row three times that in +the top row. There are three other ways of arranging the digits so as +to produce the same result. Can you find them?</p> + +<hr style="width: 30%;" /> +<p><a name="X_78_ODD_AND_EVEN_DIGITS" id="X_78_ODD_AND_EVEN_DIGITS"></a><a href="#X_78_ODD_AND_EVEN_DIGITSa"><b>78.—ODD AND EVEN DIGITS.</b></a></p> + +<p>The odd digits, 1, 3, 5, 7, and 9, add up 25, while the even figures, +2, 4, 6, and 8, only add up 20. Arrange these figures so that the odd +ones and the even ones add up alike. Complex and improper fractions +and recurring decimals are not allowed.</p> + +<hr style="width: 30%;" /> +<p><a name="X_79_THE_LOCKERS_PUZZLE" id="X_79_THE_LOCKERS_PUZZLE"></a><a href="#X_79_THE_LOCKERS_PUZZLEa"><b>79—THE LOCKERS PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/q079.png" width="500" height="180" alt="" title="" /> +</div> + +<p>A man had in his office three cupboards, each containing nine lockers, +as shown in the diagram. He told his clerk to place a different +one-figure number on each locker of cupboard A, and to do the same in +the case of B, and of C. As we are here allowed to call nought a +digit, and he was not prohibited from using nought as a number, he +clearly had the option of omitting any one of ten digits from each +cupboard.</p> + +<p>Now, the employer did not say the lockers were to be numbered in any +numerical order, and he was surprised to find, when the work was done, +that the figures had apparently been mixed up indiscriminately. +Calling upon his clerk for an explanation, the eccentric lad stated +that the notion had occurred to him so to arrange the figures that in +each case they formed a simple addition sum, the two upper rows of +figures producing the sum in the lowest row. But the most surprising +point was this: that he had so arranged them that the addition in A +gave the smallest possible sum, that the addition in C gave the +largest possible sum, and that all the nine digits in the three totals +were different. The puzzle is to show how this could be done. No +decimals are allowed and the nought may not appear in the hundreds +place.</p> + +<hr style="width: 30%;" /> +<p><a name="X_80_THE_THREE_GROUPS" id="X_80_THE_THREE_GROUPS"></a><a href="#X_80_THE_THREE_GROUPSa"><b>80.—THE THREE GROUPS.</b></a></p> + +<p>There appeared in "Nouvelles Annales de Mathématiques" the following +puzzle as a modification of one of my "Canterbury Puzzles." Arrange +the nine digits in three groups of two, three, and four digits, so +that the first two numbers when multiplied together make the third. +Thus, 12 × 483 = 5,796. I now also propose to include the cases where +there are one, four, and four digits, such as 4 × 1,738 = 6,952. Can +you find all the possible solutions in both cases?</p> + +<hr style="width: 30%;" /> +<p><a name="X_81_THE_NINE_COUNTERS" id="X_81_THE_NINE_COUNTERS"></a><a href="#X_81_THE_NINE_COUNTERSa"><b>81.—THE NINE COUNTERS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q081.png" width="400" height="137" alt="" title="" /> +</div> + +<p>I have nine counters, each bearing one of the nine digits, 1, 2, 3, 4, +5, 6, 7, 8 and 9. I arranged them on the table in two groups, as shown +in the illustration, so as to form two multiplication sums, and found +that both sums gave the same product. You will find that 158 +multiplied by 23 is 3,634, and that 79 multiplied by 46 is also 3,634. +Now, the puzzle I propose is to rearrange the counters so as to get as +large a product as possible. What is the best way of placing them? +Remember both groups must multiply to the same amount, and there must +be three counters multiplied by two in one case, and two multiplied by +two counters in the other, just as at present.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 15<a name="Page_15" id="Page_15"></a></span><a name="X_82_THE_TEN_COUNTERS" id="X_82_THE_TEN_COUNTERS"></a><a href="#X_82_THE_TEN_COUNTERSa"><b>82.—THE TEN COUNTERS.</b></a></p> + +<p>In this case we use the nought in addition to the 1, 2, 3, 4, 5, 6, 7, +8, 9. The puzzle is, as in the last case, so to arrange the ten +counters that the products of the two multiplications shall be the +same, and you may here have one or more figures in the multiplier, as +you choose. The above is a very easy feat; but it is also required to +find the two arrangements giving pairs of the highest and lowest +products possible. Of course every counter must be used, and the +cipher may not be placed to the left of a row of figures where it +would have no effect. Vulgar fractions or decimals are not allowed.</p> + +<hr style="width: 30%;" /> +<p><a name="X_83_DIGITAL_MULTIPLICATION" id="X_83_DIGITAL_MULTIPLICATION"></a><a href="#X_83_DIGITAL_MULTIPLICATIONa"><b>83.—DIGITAL MULTIPLICATION.</b></a></p> + +<p>Here is another entertaining problem with the nine digits, the nought +being excluded. Using each figure once, and only once, we can form two +multiplication sums that have the same product, and this may be done +in many ways. For example, 7x658 and 14x329 contain all the digits +once, and the product in each case is the same—4,606. Now, it will be +seen that the sum of the digits in the product is 16, which is neither +the highest nor the lowest sum so obtainable. Can you find the +solution of the problem that gives the lowest possible sum of digits +in the common product? Also that which gives the highest possible sum?</p> + +<hr style="width: 30%;" /> +<p><a name="X_84_THE_PIERROTS_PUZZLE" id="X_84_THE_PIERROTS_PUZZLE"></a><a href="#X_84_THE_PIERROTS_PUZZLEa"><b>84.—THE PIERROT'S PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/q084.png" width="500" height="209" alt="" title="" /> +</div> + +<p>The Pierrot in the illustration is standing in a posture that +represents the sign of multiplication. He is indicating the peculiar +fact that 15 multiplied by 93 produces exactly the same figures +(1,395), differently arranged. The puzzle is to take any four digits +you like (all different) and similarly arrange them so that the number +formed on one side of the Pierrot when multiplied by the number on the +other side shall produce the same figures. There are very few ways of +doing it, and I shall give all the cases possible. Can you find them +all? You are allowed to put two figures on each side of the Pierrot as +in the example shown, or to place a single figure on one side and +three figures on the other. If we only used three digits instead of +four, the only possible ways are these: 3 multiplied by 51 equals 153, +and 6 multiplied by 21 equals 126.</p> + +<hr style="width: 30%;" /> +<p><a name="X_85_THE_CAB_NUMBERS" id="X_85_THE_CAB_NUMBERS"></a><a href="#X_85_THE_CAB_NUMBERSa"><b>85.—THE CAB NUMBERS.</b></a></p> + +<p>A London policeman one night saw two cabs drive off in opposite +directions under suspicious circumstances. This officer was a +particularly careful and wide-awake man, and he took out his +pocket-book to make an entry of the numbers of the cabs, but +discovered that he had lost his pencil. Luckily, however, he found a +small piece of chalk, with which he marked the two numbers on the +gateway of a wharf close by. When he returned to the same spot on his +beat he stood and looked again at the numbers, and noticed this +peculiarity, that all the nine digits (no nought) were used and that +no figure was repeated, but that if he multiplied the two numbers +together they again produced the nine digits, all once, and once only. +When one of the clerks arrived at the wharf in the early morning, he +observed the chalk marks and carefully rubbed them out. As the +policeman could not remember them, certain mathematicians were then +consulted as to whether there was any known method for discovering all +the pairs of numbers that have the peculiarity that the officer had +noticed; but they knew of none. The investigation, however, was +interesting, and the following question out of many was proposed: What +two numbers, containing together all the nine digits, will, when +multiplied together, produce another number (the <i>highest possible</i>) +containing also all the nine digits? The nought is not allowed +anywhere.</p> + +<hr style="width: 30%;" /> +<p><a name="X_86_QUEER_MULTIPLICATION" id="X_86_QUEER_MULTIPLICATION"></a><a href="#X_86_QUEER_MULTIPLICATIONa"><b>86.—QUEER MULTIPLICATION.</b></a></p> + +<p>If I multiply 51,249,876 by 3 (thus using all the nine digits once, +and once only), I get 153,749,628 (which again contains all the nine +digits once). Similarly, if I multiply 16,583,742 by 9 the <span class='pagenum'>Pg 16<a name="Page_16" id="Page_16"></a></span>result is +149,253,678, where in each case all the nine digits are used. Now, +take 6 as your multiplier and try to arrange the remaining eight +digits so as to produce by multiplication a number containing all nine +once, and once only. You will find it far from easy, but it can be +done.</p> + +<hr style="width: 30%;" /> +<p><a name="X_87_THE_NUMBER_CHECKS_PUZZLE" id="X_87_THE_NUMBER_CHECKS_PUZZLE"></a><a href="#X_87_THE_NUMBER_CHECKS_PUZZLEa"><b>87.—THE NUMBER CHECKS PUZZLE.</b></a></p> + +<p>Where a large number of workmen are employed on a building it is +customary to provide every man with a little disc bearing his number. +These are hung on a board by the men as they arrive, and serve as a +check on punctuality. Now, I once noticed a foreman remove a number of +these checks from his board and place them on a split-ring which he +carried in his pocket. This at once gave me the idea for a good +puzzle. In fact, I will confide to my readers that this is just how +ideas for puzzles arise. You cannot really create an idea: it +happens—and you have to be on the alert to seize it when it does so +happen.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q087.png" width="400" height="335" alt="" title="" /> +</div> + +<p>It will be seen from the illustration that there are ten of these +checks on a ring, numbered 1 to 9 and 0. The puzzle is to divide them +into three groups without taking any off the ring, so that the first +group multiplied by the second makes the third group. For example, we +can divide them into the three groups, 2—8 9 7—1 5 4 6 3, by +bringing the 6 and the 3 round to the 4, but unfortunately the first +two when multiplied together do not make the third. Can you separate +them correctly? Of course you may have as many of the checks as you +like in any group. The puzzle calls for some ingenuity, unless you +have the luck to hit on the answer by chance.</p> + +<hr style="width: 30%;" /> +<p><a name="X_88_DIGITAL_DIVISION" id="X_88_DIGITAL_DIVISION"></a><a href="#X_88_DIGITAL_DIVISIONa"><b>88.—DIGITAL DIVISION.</b></a></p> + +<p>It is another good puzzle so to arrange the nine digits (the nought +excluded) into two groups so that one group when divided by the other +produces a given number without remainder. For example, 1 3 4 5 8 +divided by 6 7 2 9 gives 2. Can the reader find similar arrangements +producing 3, 4, 5, 6, 7, 8, and 9 respectively? Also, can he find the +pairs of smallest possible numbers in each case? Thus, 1 4 6 5 8 +divided by 7 3 2 9 is just as correct for 2 as the other example we +have given, but the numbers are higher.</p> + +<hr style="width: 30%;" /> +<p><a name="X_89_ADDING_THE_DIGITS" id="X_89_ADDING_THE_DIGITS"></a><a href="#X_89_ADDING_THE_DIGITSa"><b>89.—ADDING THE DIGITS.</b></a></p> + +<p>If I write the sum of money, £987, 5<i>s</i>. 4½<i>d</i>.., and add up the digits, +they sum to 36. No digit has thus been used a second time in the +amount or addition. This is the largest amount possible under the +conditions. Now find the smallest possible amount, pounds, shillings, +pence, and farthings being all represented. You need not use more of +the nine digits than you choose, but no digit may be repeated +throughout. The nought is not allowed.</p> + +<hr style="width: 30%;" /> +<p><a name="X_90_THE_CENTURY_PUZZLE" id="X_90_THE_CENTURY_PUZZLE"></a><a href="#X_90_THE_CENTURY_PUZZLEa"><b>90.—THE CENTURY PUZZLE.</b></a></p> + +<p>Can you write 100 in the form of a mixed number, using all the nine +digits once, and only once? The late distinguished French +mathematician, Edouard Lucas, found seven different ways of doing it, +and expressed his doubts as to there being any other ways. As a matter +of fact there are just eleven ways and no more. Here is one of them, +91 <sup>5742</sup>/<sub>638</sub>. Nine of the other ways have similarly two figures in the +integral part of the number, but the eleventh expression has only one +figure there. Can the reader find this last form?</p> + +<hr style="width: 30%;" /> +<p><a name="X_91_MORE_MIXED_FRACTIONS" id="X_91_MORE_MIXED_FRACTIONS"></a><a href="#X_91_MORE_MIXED_FRACTIONSa"><b>91.—MORE MIXED FRACTIONS.</b></a></p> + +<p>When I first published my solution to the last puzzle, I was led to +attempt the expression of all numbers in turn up to 100 by a mixed +fraction containing all the nine digits. Here are twelve numbers for +the reader to try his hand at: 13, 14, 15, 16, 18, 20, 27, 36, 40, 69, +72, 94. Use every one of the nine digits once, and only once, in every +case.</p> + +<hr style="width: 30%;" /> +<p><a name="X_92_DIGITAL_SQUARE_NUMBERS" id="X_92_DIGITAL_SQUARE_NUMBERS"></a><a href="#X_92_DIGITAL_SQUARE_NUMBERSa"><b>92.—DIGITAL SQUARE NUMBERS.</b></a></p> + +<p>Here are the nine digits so arranged that they form four square +numbers: 9, 81, 324, 576. Now, can you put them all together so as to +form a single square number—(I) the smallest possible, and (II) the +largest possible?</p> + +<hr style="width: 30%;" /> +<p><a name="X_93_THE_MYSTIC_ELEVEN" id="X_93_THE_MYSTIC_ELEVEN"></a><a href="#X_93_THE_MYSTIC_ELEVENa"><b>93.—THE MYSTIC ELEVEN.</b></a></p> + +<p>Can you find the largest possible number containing any nine of the +ten digits (calling nought a digit) that can be divided by 11 without +a remainder? Can you also find the smallest possible number produced +in the same way that is divisible by 11? Here is an example, where the +digit 5 has been omitted: 896743012. This number contains nine of the +digits and is divisible by 11, but it is neither the largest nor the +smallest number that will work.</p> + +<hr style="width: 30%;" /> +<p><a name="X_94_THE_DIGITAL_CENTURY" id="X_94_THE_DIGITAL_CENTURY"></a><a href="#X_94_THE_DIGITAL_CENTURYa"><b>94.—THE DIGITAL CENTURY.</b></a></p> + +<p>1 2 3 4 5 6 7 8 9 = 100.</p> + +<p>It is required to place arithmetical signs between the nine figures so +that they shall equal <span class='pagenum'>Pg 17<a name="Page_17" id="Page_17"></a></span>100. Of course, you must not alter the present +numerical arrangement of the figures. Can you give a correct solution +that employs (1) the fewest possible signs, and (2) the fewest +possible separate strokes or dots of the pen? That is, it is necessary +to use as few signs as possible, and those signs should be of the +simplest form. The signs of addition and multiplication (+ and ×) will +thus count as two strokes, the sign of subtraction (-) as one stroke, +the sign of division (÷) as three, and so on.</p> + +<hr style="width: 30%;" /> +<p><a name="X_95_THE_FOUR_SEVENS" id="X_95_THE_FOUR_SEVENS"></a><a href="#X_95_THE_FOUR_SEVENSa"><b>95.—THE FOUR SEVENS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q095.png" width="400" height="500" alt="" title="" /> +</div> + +<p>In the illustration Professor Rackbrane is seen demonstrating one of +the little posers with which he is accustomed to entertain his class. +He believes that by taking his pupils off the beaten tracks he is the +better able to secure their attention, and to induce original and +ingenious methods of thought. He has, it will be seen, just shown how +four 5's may be written with simple arithmetical signs so as to +represent 100. Every juvenile reader will see at a glance that his +example is quite correct. Now, what he wants you to do is this: +Arrange four 7's (neither more nor less) with arithmetical signs so +that they shall represent 100. If he had said we were to use four 9's +we might at once have written 99<sup>9</sup>/<sub>9</sub>, but the four 7's call for rather +more ingenuity. Can you discover the little trick?</p> + +<hr style="width: 30%;" /> +<p><a name="X_96_THE_DICE_NUMBERS" id="X_96_THE_DICE_NUMBERS"></a><a href="#X_96_THE_DICE_NUMBERSa"><b>96.—THE DICE NUMBERS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q096.png" width="400" height="140" alt="" title="" /> +</div> + +<p>I have a set of four dice, not marked with spots in the ordinary way, +but with Arabic figures, as shown in the illustration. Each die, of +course, bears the numbers 1 to 6. When put together they will form a +good many, different numbers. As represented they make the number +1246. Now, if I make all the different four-figure numbers that are +possible with these dice (never putting the same figure more than once +in any number), what will they all add up to? You are allowed to turn +the 6 upside down, so as to represent a 9. I do not ask, or expect, +the reader to go to all the labour of writing out the full list of +numbers and then adding them up. Life is not long enough for such +wasted energy. Can you get at the answer in any other way?</p> + + + +<hr style="width: 65%;" /> +<h2><a name="VARIOUS_ARITHMETICAL_AND_ALGEBRAICAL_PROBLEMS" id="VARIOUS_ARITHMETICAL_AND_ALGEBRAICAL_PROBLEMS"></a><a href="#CONTENTS">VARIOUS ARITHMETICAL AND ALGEBRAICAL PROBLEMS.</a></h2> + +<p class='center'> +<span style="margin-left: 0em">"Variety's the very spice of life,<br /></span> +<span style="margin-left: 0em">That gives it all its flavour."<br /></span> +<span style="margin-left: 8em">COWPER: <i>The Task.</i><br /></span> +</p> + +<hr style="width: 30%;" /> +<p><a name="X_97_THE_SPOT_ON_THE_TABLE" id="X_97_THE_SPOT_ON_THE_TABLE"></a><a href="#X_97_THE_SPOT_ON_THE_TABLEa"><b>97.—THE SPOT ON THE TABLE.</b></a></p> + +<p>A boy, recently home from school, wished to give his father an +exhibition of his precocity. He pushed a large circular table into the +corner of the room, as shown in the illustration, so that it touched +both walls, and he then pointed to a spot of ink on the extreme edge.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q097.png" width="400" height="398" alt="" title="" /> +</div> + +<p>"Here is a little puzzle for you, pater," said the youth. "That spot +is exactly eight inches from one wall and nine inches from the other. +Can you tell me the diameter of the table without measuring it?"</p> + +<p>The boy was overheard to tell a friend, "It <span class='pagenum'>Pg 18<a name="Page_18" id="Page_18"></a></span>fairly beat the guv'nor;" +but his father is known to have remarked to a City acquaintance that +he solved the thing in his head in a minute. I often wonder which +spoke the truth.</p> + +<hr style="width: 30%;" /> +<p><a name="X_98_ACADEMIC_COURTESIES" id="X_98_ACADEMIC_COURTESIES"></a><a href="#X_98_ACADEMIC_COURTESIESa"><b>98.—ACADEMIC COURTESIES.</b></a></p> + +<p>In a certain mixed school, where a special feature was made of the +inculcation of good manners, they had a curious rule on assembling +every morning. There were twice as many girls as boys. Every girl made +a bow to every other girl, to every boy, and to the teacher. Every boy +made a bow to every other boy, to every girl, and to the teacher. In +all there were nine hundred bows made in that model academy every +morning. Now, can you say exactly how many boys there were in the +school? If you are not very careful, you are likely to get a good deal +out in your calculation.</p> + +<hr style="width: 30%;" /> +<p><a name="X_99_THE_THIRTY-THREE_PEARLS" id="X_99_THE_THIRTY-THREE_PEARLS"></a><a href="#X_99_THE_THIRTY-THREE_PEARLSa"><b>99.—THE THIRTY-THREE PEARLS.</b></a></p> + +<p>"A man I know," said Teddy Nicholson at a certain family party, +"possesses a string of thirty-three pearls. The middle pearl is the +largest and best of all, and the others are so selected and arranged +that, starting from one end, each successive pearl is worth £100 more +than the preceding one, right up to the big pearl. From the other end +the pearls increase in value by £150 up to the large pearl. The whole +string is worth £65,000. What is the value of that large pearl?"</p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/q099.png" width="300" height="668" alt="" title="" /> +</div> + +<p>"Pearls and other articles of clothing," said Uncle Walter, when the +price of the precious gem had been discovered, "remind me of Adam and +Eve. Authorities, you may not know, differ as to the number of apples +that were eaten by Adam and Eve. It is the opinion of some that Eve 8 +(ate) and Adam 2 (too), a total of 10 only. But certain mathematicians +have figured it out differently, and hold that Eve 8 and Adam a total +of 16. Yet the most recent investigators think the above figures +entirely wrong, for if Eve 8 and Adam 8 2, the total must be 90."</p> + +<p>"Well," said Harry, "it seems to me that if there were giants in those +days, probably Eve 8 1 and Adam 8 2, which would give a total of 163."</p> + +<p>"I am not at all satisfied," said Maud. "It seems to me that if Eve 8 +1 and Adam 8 1 2, they together consumed 893."</p> + +<p>"I am sure you are all wrong," insisted Mr. Wilson, "for I consider +that Eve 8 1 4 Adam, and Adam 8 1 2 4 Eve, so we get a total of +8,938."</p> + +<p>"But, look here," broke in Herbert. "If Eve 8 1 4 Adam and Adam 8 1 2 +4 2 oblige Eve, surely the total must have been 82,056!"</p> + +<p>At this point Uncle Walter suggested that they might let the matter +rest. He declared it to be clearly what mathematicians call an +indeterminate problem.</p> + +<hr style="width: 30%;" /> +<p><a name="X_100_THE_LABOURERS_PUZZLE" id="X_100_THE_LABOURERS_PUZZLE"></a><a href="#X_100_THE_LABOURERS_PUZZLEa"><b>100.—THE LABOURER'S PUZZLE.</b></a></p> + +<p>Professor Rackbrane, during one of his rambles, chanced to come upon a +man digging a deep hole.</p> + +<p>"Good morning," he said. "How deep is that hole?"</p> + +<p>"Guess," replied the labourer. "My height is exactly five feet ten +inches."</p> + +<p>"How much deeper are you going?" said the professor.</p> + +<p>"I am going twice as deep," was the answer, "and then my head will be +twice as far below ground as it is now above ground."</p> + +<p>Rackbrane now asks if you could tell how deep that hole would be when +finished.</p> + +<hr style="width: 30%;" /> +<p><a name="X_101_THE_TRUSSES_OF_HAY" id="X_101_THE_TRUSSES_OF_HAY"></a><a href="#X_101_THE_TRUSSES_OF_HAYa"><b>101.—THE TRUSSES OF HAY.</b></a></p> + +<p>Farmer Tompkins had five trusses of hay, which he told his man Hodge +to weigh before delivering them to a customer. The stupid fellow +weighed them two at a time in all possible ways, and informed his +master that the weights in pounds were 110, 112, 113, 114, 115, 116, +117, 118, 120, and 121. Now, how was Farmer Tompkins to find out from +these figures how much every one of the five trusses weighed singly? +The reader may at first think that he ought to be told "which pair is +which pair," or something of that sort, but it is quite unnecessary. +Can you give the five correct weights?</p> + +<hr style="width: 30%;" /> +<p><a name="X_102_MR_GUBBINS_IN_A_FOG" id="X_102_MR_GUBBINS_IN_A_FOG"></a><a href="#X_102_MR_GUBBINS_IN_A_FOGa"><b>102.—MR. GUBBINS IN A FOG.</b></a></p> + +<p>Mr. Gubbins, a diligent man of business, was much inconvenienced by a +London fog. The electric light happened to be out of order and he had +to manage as best he could with two candles. His clerk assured him +that though <span class='pagenum'>Pg 19<a name="Page_19" id="Page_19"></a></span>both were of the same length one candle would burn for +four hours and the other for five hours. After he had been working +some time he put the candles out as the fog had lifted, and he then +noticed that what remained of one candle was exactly four times the +length of what was left of the other.</p> + +<p>When he got home that night Mr. Gubbins, who liked a good puzzle, said +to himself, "Of course it is possible to work out just how long those +two candles were burning to-day. I'll have a shot at it." But he soon +found himself in a worse fog than the atmospheric one. Could you have +assisted him in his dilemma? How long were the candles burning?</p> + +<hr style="width: 30%;" /> +<p><a name="X_103_PAINTING_THE_LAMP-POSTS" id="X_103_PAINTING_THE_LAMP-POSTS"></a><a href="#X_103_PAINTING_THE_LAMP-POSTSa"><b>103.—PAINTING THE LAMP-POSTS.</b></a></p> + +<p>Tim Murphy and Pat Donovan were engaged by the local authorities to +paint the lamp-posts in a certain street. Tim, who was an early riser, +arrived first on the job, and had painted three on the south side when +Pat turned up and pointed out that Tim's contract was for the north +side. So Tim started afresh on the north side and Pat continued on the +south. When Pat had finished his side he went across the street and +painted six posts for Tim, and then the job was finished. As there was +an equal number of lamp-posts on each side of the street, the simple +question is: Which man painted the more lamp-posts, and just how many +more?</p> + +<hr style="width: 30%;" /> +<p><a name="X_104_CATCHING_THE_THIEF" id="X_104_CATCHING_THE_THIEF"></a><a href="#X_104_CATCHING_THE_THIEFa"><b>104.—CATCHING THE THIEF.</b></a></p> + +<p>"Now, constable," said the defendant's counsel in cross-examination," +you say that the prisoner was exactly twenty-seven steps ahead of you +when you started to run after him?"</p> + +<p>"Yes, sir."</p> + +<p>"And you swear that he takes eight steps to your five?"</p> + +<p>"That is so."</p> + +<p>"Then I ask you, constable, as an intelligent man, to explain how you +ever caught him, if that is the case?"</p> + +<p>"Well, you see, I have got a longer stride. In fact, two of my steps +are equal in length to five of the prisoner's. If you work it out, you +will find that the number of steps I required would bring me exactly +to the spot where I captured him."</p> + +<p>Here the foreman of the jury asked for a few minutes to figure out the +number of steps the constable must have taken. Can you also say how +many steps the officer needed to catch the thief?</p> + +<hr style="width: 30%;" /> +<p><a name="X_105_THE_PARISH_COUNCIL_ELECTION" id="X_105_THE_PARISH_COUNCIL_ELECTION"></a><a href="#X_105_THE_PARISH_COUNCIL_ELECTIONa"><b>105.—THE PARISH COUNCIL ELECTION.</b></a></p> + +<p>Here is an easy problem for the novice. At the last election of the +parish council of Tittlebury-in-the-Marsh there were twenty-three +candidates for nine seats. Each voter was qualified to vote for nine +of these candidates or for any less number. One of the electors wants +to know in just how many different ways it was possible for him to +vote.</p> + +<hr style="width: 30%;" /> +<p><a name="X_106_THE_MUDDLETOWN_ELECTION" id="X_106_THE_MUDDLETOWN_ELECTION"></a><a href="#X_106_THE_MUDDLETOWN_ELECTIONa"><b>106.—THE MUDDLETOWN ELECTION.</b></a></p> + +<p>At the last Parliamentary election at Muddletown 5,473 votes were +polled. The Liberal was elected by a majority of 18 over the +Conservative, by 146 over the Independent, and by 575 over the +Socialist. Can you give a simple rule for figuring out how many votes +were polled for each candidate?</p> + +<hr style="width: 30%;" /> +<p><a name="X_107_THE_SUFFRAGISTS_MEETING" id="X_107_THE_SUFFRAGISTS_MEETING"></a><a href="#X_107_THE_SUFFRAGISTS_MEETINGa"><b>107.—THE SUFFRAGISTS' MEETING.</b></a></p> + +<p>At a recent secret meeting of Suffragists a serious difference of +opinion arose. This led to a split, and a certain number left the +meeting. "I had half a mind to go myself," said the chair-woman, "and +if I had done so, two-thirds of us would have retired." "True," said +another member; "but if I had persuaded my friends Mrs. Wild and +Christine Armstrong to remain we should only have lost half our +number." Can you tell how many were present at the meeting at the +start?</p> + +<hr style="width: 30%;" /> +<p><a name="X_108_THE_LEAP-YEAR_LADIES" id="X_108_THE_LEAP-YEAR_LADIES"></a><a href="#X_108_THE_LEAP-YEAR_LADIESa"><b>108.—THE LEAP-YEAR LADIES.</b></a></p> + +<p>Last leap-year ladies lost no time in exercising the privilege of +making proposals of marriage. If the figures that reached me from an +occult source are correct, the following represents the state of +affairs in this country.</p> + +<p>A number of women proposed once each, of whom one-eighth were widows. +In consequence, a number of men were to be married of whom +one-eleventh were widowers. Of the proposals made to widowers, +one-fifth were declined. All the widows were accepted. Thirty-five +forty-fourths of the widows married bachelors. One thousand two +hundred and twenty-one spinsters were declined by bachelors. The +number of spinsters accepted by bachelors was seven times the number +of widows accepted by bachelors. Those are all the particulars that I +was able to obtain. Now, how many women proposed?</p> + +<hr style="width: 30%;" /> +<p><a name="X_109_THE_GREAT_SCRAMBLE" id="X_109_THE_GREAT_SCRAMBLE"></a><a href="#X_109_THE_GREAT_SCRAMBLEa"><b>109.—THE GREAT SCRAMBLE.</b></a></p> + +<p>After dinner, the five boys of a household happened to find a parcel +of sugar-plums. It was quite unexpected loot, and an exciting scramble +ensued, the full details of which I will recount with accuracy, as it +forms an interesting puzzle.</p> + +<p>You see, Andrew managed to get possession of just two-thirds of the +parcel of sugar-plums. Bob at once grabbed three-eighths of these, and +Charlie managed to seize three-tenths also. Then young David dashed +upon the scene, and captured all that Andrew had left, except +one-seventh, which Edgar artfully secured for himself by a cunning +trick. Now the fun began in real earnest, for Andrew and Charlie +jointly set upon Bob, who stumbled against the fender and dropped half +of all that he had, which were equally picked up by David and Edgar, +who had crawled under a table and were waiting. Next, Bob sprang on +Charlie from a chair, and upset all the latter's collection on to the +floor. Of this prize Andrew got just a quarter, Bob <span class='pagenum'>Pg 20<a name="Page_20" id="Page_20"></a></span>gathered up +one-third, David got two-sevenths, while Charlie and Edgar divided +equally what was left of that stock.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q109.png" width="400" height="454" alt="" title="" /> +</div> + +<p>They were just thinking the fray was over when David suddenly struck +out in two directions at once, upsetting three-quarters of what Bob +and Andrew had last acquired. The two latter, with the greatest +difficulty, recovered five-eighths of it in equal shares, but the +three others each carried off one-fifth of the same. Every sugar-plum +was now accounted for, and they called a truce, and divided equally +amongst them the remainder of the parcel. What is the smallest number +of sugar-plums there could have been at the start, and what proportion +did each boy obtain?</p> + +<hr style="width: 30%;" /> +<p><a name="X_110_THE_ABBOTS_PUZZLE" id="X_110_THE_ABBOTS_PUZZLE"></a><a href="#X_110_THE_ABBOTS_PUZZLEa"><b>110.—THE ABBOT'S PUZZLE.</b></a></p> + +<p>The first English puzzlist whose name has come down to us was a +Yorkshireman—no other than Alcuin, Abbot of Canterbury (A.D. +735-804). Here is a little puzzle from his works, which is at least +interesting on account of its antiquity. "If 100 bushels of corn were +distributed among 100 people in such a manner that each man received +three bushels, each woman two, and each child half a bushel, how many +men, women, and children were there?"</p> + +<p>Now, there are six different correct answers, if we exclude a case +where there would be no women. But let us say that there were just +five times as many women as men, then what is the correct solution?</p> + +<hr style="width: 30%;" /> +<p><a name="X_111_REAPING_THE_CORN" id="X_111_REAPING_THE_CORN"></a><a href="#X_111_REAPING_THE_CORNa"><b>111.—REAPING THE CORN.</b></a></p> + +<p>A farmer had a square cornfield. The corn was all ripe for reaping, +and, as he was short of men, it was arranged that he and his son +should share the work between them. The farmer first cut one rod wide +all round the square, thus leaving a smaller square of standing corn +in the middle of the field. "Now," he said to his son, "I have cut my +half of the field, and you can do your share." The son was not quite +satisfied as to the proposed division of labour, and as the village +schoolmaster happened to be passing, he appealed to that person to +decide the matter. He found the farmer was quite correct, provided +there was no dispute as to the size of the field, and on this point +they were agreed. Can you tell the area of the field, as that +ingenious schoolmaster succeeded in doing?</p> + +<hr style="width: 30%;" /> +<p><a name="X_112_A_PUZZLING_LEGACY" id="X_112_A_PUZZLING_LEGACY"></a><a href="#X_112_A_PUZZLING_LEGACYa"><b>112.—A PUZZLING LEGACY.</b></a></p> + +<p>A man left a hundred acres of land to be divided among his three +sons—Alfred, Benjamin, and Charles—in the proportion of one-third, +one-fourth, and one-fifth respectively. But Charles died. How was the +land to be divided fairly between Alfred and Benjamin?</p> +<hr style="width: 30%;" /> +<p><a name="X_113_THE_TORN_NUMBER" id="X_113_THE_TORN_NUMBER"></a><a href="#X_113_THE_TORN_NUMBERa"><b>113.—THE TORN NUMBER.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q113.png" width="400" height="165" alt="" title="" /> +</div> + +<p>I had the other day in my possession a label bearing the number 3 0 2 5 +in large figures. This got accidentally torn in half, so that 3 0 was on +one piece and 2 5 on the other, as shown on the illustration. On +looking at these pieces I began to make a calculation, scarcely +conscious of what I was doing, when I discovered this little +peculiarity. If we add the 3 and the 2 5 together and square the sum +we get as the result the complete original number on the label! Thus, +30 added to 25 is 55, and 55 multiplied by 55 is 3025. Curious, is it +not? Now, the puzzle is to find another number, composed of four +figures, all different, which may be divided in the middle and produce +the same result.</p> + +<hr style="width: 30%;" /> +<p><a name="X_114_CURIOUS_NUMBERS" id="X_114_CURIOUS_NUMBERS"></a><a href="#X_114_CURIOUS_NUMBERSa"><b>114.—CURIOUS NUMBERS.</b></a></p> + +<p>The number 48 has this peculiarity, that if you add 1 to it the result +is a square number (49, the square of 7), and if you add 1 to its +half, you also get a square number (25, the square of 5). Now, there +is no limit to the numbers that have this peculiarity, and it is an +interesting puzzle to find three more of them—the smallest possible +numbers. What are they?</p> + +<hr style="width: 30%;" /> +<p><a name="X_115_A_PRINTERS_ERROR" id="X_115_A_PRINTERS_ERROR"></a><a href="#X_115_A_PRINTERS_ERRORa"><b>115.—A PRINTER'S ERROR.</b></a></p> + +<p>In a certain article a printer had to set up the figures 5<sup>4</sup> × 2<sup>3</sup>, +which, of course, means that the fourth power of 5 (625) is to be +multiplied by the cube of 2 (8), the product of which is 5,000. But he +printed 5<sup>4</sup> × 2<sup>3</sup> as 5 4 2 3, which is not correct. Can you place four +digits in the manner shown, so that it will be equally correct if the +printer sets it up aright or makes the same blunder?</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 21<a name="Page_21" id="Page_21"></a></span><a name="X_116_THE_CONVERTED_MISER" id="X_116_THE_CONVERTED_MISER"></a><a href="#X_116_THE_CONVERTED_MISERa"><b>116.—THE CONVERTED MISER.</b></a></p> + +<p>Mr. Jasper Bullyon was one of the very few misers who have ever been +converted to a sense of their duty towards their less fortunate +fellow-men. One eventful night he counted out his accumulated wealth, +and resolved to distribute it amongst the deserving poor.</p> + +<p>He found that if he gave away the same number of pounds every day in +the year, he could exactly spread it over a twelvemonth without there +being anything left over; but if he rested on the Sundays, and only +gave away a fixed number of pounds every weekday, there would be one +sovereign left over on New Year's Eve. Now, putting it at the lowest +possible, what was the exact number of pounds that he had to +distribute?</p> + +<p>Could any question be simpler? A sum of pounds divided by one number +of days leaves no remainder, but divided by another number of days +leaves a sovereign over. That is all; and yet, when you come to tackle +this little question, you will be surprised that it can become so +puzzling.</p> + +<hr style="width: 30%;" /> +<p><a name="X_117_A_FENCE_PROBLEM" id="X_117_A_FENCE_PROBLEM"></a><a href="#X_117_A_FENCE_PROBLEMa"><b>117.—A FENCE PROBLEM.</b></a></p> + +<p>The practical usefulness of puzzles is a point that we are liable to +overlook. Yet, as a matter of fact, I have from time to time received +quite a large number of letters from individuals who have found that +the mastering of some little principle upon which a puzzle was built +has proved of considerable value to them in a most unexpected way. +Indeed, it may be accepted as a good maxim that a puzzle is of little +real value unless, as well as being amusing and perplexing, it +conceals some instructive and possibly useful feature. It is, however, +very curious how these little bits of acquired knowledge dovetail into +the occasional requirements of everyday life, and equally curious to +what strange and mysterious uses some of our readers seem to apply +them. What, for example, can be the object of Mr. Wm. Oxley, who +writes to me all the way from Iowa, in wishing to ascertain the +dimensions of a field that he proposes to enclose, containing just as +many acres as there shall be rails in the fence?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q117.png" width="400" height="341" alt="" title="" /> +</div> + +<p>The man wishes to fence in a perfectly square field which is to +contain just as many acres as there are rails in the required fence. +Each hurdle, or portion of fence, is seven rails high, and two lengths +would extend one pole (16½ ft.): that is to say, there are fourteen +rails to the pole, lineal measure. Now, what must be the size of the +field?</p> + +<hr style="width: 30%;" /> +<p><a name="X_118_CIRCLING_THE_SQUARES" id="X_118_CIRCLING_THE_SQUARES"></a><a href="#X_118_CIRCLING_THE_SQUARESa"><b>118.—CIRCLING THE SQUARES.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q118.png" width="400" height="412" alt="" title="" /> +</div> + +<p>The puzzle is to place a different number in each of the ten squares +so that the sum of the squares of any two adjacent numbers shall be +equal to the sum of the squares of the two numbers diametrically +opposite to them. The four numbers placed, as examples, must stand as +they are. The square of 16 is 256, and the square of 2 is 4. Add these +together, and the result is 260. Also—the square of 14 is 196, and +the square of 8 is 64. These together also make 260. Now, in precisely +the same way, B and C should be equal to G and H (the sum will not +necessarily be 260), A and K to F and E, H and I to C and D, and so +on, with any two adjoining squares in the circle.</p> + +<p>All you have to do is to fill in the remaining six numbers. Fractions +are not allowed, and I shall show that no number need contain more +than two figures.</p> + +<hr style="width: 30%;" /> +<p><a name="X_119_RACKBRANES_LITTLE_LOSS" id="X_119_RACKBRANES_LITTLE_LOSS"></a><a href="#X_119_RACKBRANES_LITTLE_LOSSa"><b>119.—RACKBRANE'S LITTLE LOSS.</b></a></p> + +<p>Professor Rackbrane was spending an evening with his old friends, Mr. +and Mrs. Potts, and they engaged in some game (he does not say what +game) of cards. The professor lost the first game, which resulted in +doubling the money that both Mr. and Mrs. Potts had laid on the table. +The second game was lost by Mrs. Potts, which doubled the money then +held by her husband and the professor. Curiously enough, the third +game was lost by Mr. Potts, and had the <span class='pagenum'>Pg 22<a name="Page_22" id="Page_22"></a></span>effect of doubling the money +then held by his wife and the professor. It was then found that each +person had exactly the same money, but the professor had lost five +shillings in the course of play. Now, the professor asks, what was the +sum of money with which he sat down at the table? Can you tell him?</p> + +<hr style="width: 30%;" /> +<p><a name="X_120_THE_FARMER_AND_HIS_SHEEP" id="X_120_THE_FARMER_AND_HIS_SHEEP"></a><a href="#X_120_THE_FARMER_AND_HIS_SHEEPa"><b>120.—THE FARMER AND HIS SHEEP.</b></a></p> + +<div class="figcenter" style="width: 550px;"> +<img src="images/q120.png" width="550" height="391" alt="" title="" /> +</div> + +<p>Farmer Longmore had a curious aptitude for arithmetic, and was known +in his district as the "mathematical farmer." The new vicar was not +aware of this fact when, meeting his worthy parishioner one day in the +lane, he asked him in the course of a short conversation, "Now, how +many sheep have you altogether?" He was therefore rather surprised at +Longmore's answer, which was as follows: "You can divide my sheep into +two different parts, so that the difference between the two numbers is +the same as the difference between their squares. Maybe, Mr. Parson, +you will like to work out the little sum for yourself."</p> + +<p>Can the reader say just how many sheep the farmer had? Supposing he +had possessed only twenty sheep, and he divided them into the two +parts 12 and 8. Now, the difference between their squares, 144 and 64, +is 80. So that will not do, for 4 and 80 are certainly not the same. +If you can find numbers that work out correctly, you will know exactly +how many sheep Farmer Longmore owned.</p> + +<hr style="width: 30%;" /> +<p><a name="X_121_HEADS_OR_TAILS" id="X_121_HEADS_OR_TAILS"></a><a href="#X_121_HEADS_OR_TAILSa"><b>121.—HEADS OR TAILS.</b></a></p> + +<p>Crooks, an inveterate gambler, at Goodwood recently said to a friend, +"I'll bet you half the money in my pocket on the toss of a coin—heads +I win, tails I lose." The coin was tossed and the money handed over. +He repeated the offer again and again, each time betting half the +money then in his possession. We are not told how long the game went +on, or how many times the coin was tossed, but this we know, that the +number of times that Crooks lost was exactly equal to the number of +times that he won. Now, did he gain or lose by this little venture?</p> + +<hr style="width: 30%;" /> +<p><a name="X_122_THE_SEE-SAW_PUZZLE" id="X_122_THE_SEE-SAW_PUZZLE"></a><a href="#X_122_THE_SEE-SAW_PUZZLEa"><b>122.—THE SEE-SAW PUZZLE.</b></a></p> + +<p>Necessity is, indeed, the mother of invention. I was amused the other +day in watching a boy who wanted to play see-saw and, in his failure +to find another child to share the sport with him, had been driven +back upon the ingenious resort of tying a number of bricks to one end +of the plank to balance his weight at the other.</p> + +<p>As a matter of fact, he just balanced against sixteen bricks, when +these were fixed to the short end of plank, but if he fixed them to +the long end of plank he only needed eleven as balance.</p> + +<p>Now, what was that boy's weight, if a brick <span class='pagenum'>Pg 23<a name="Page_23" id="Page_23"></a></span>weighs equal to a +three-quarter brick and three-quarters of a pound?</p> + +<hr style="width: 30%;" /> +<p><a name="X_123_A_LEGAL_DIFFICULTY" id="X_123_A_LEGAL_DIFFICULTY"></a><a href="#X_123_A_LEGAL_DIFFICULTYa"><b>123.—A LEGAL DIFFICULTY.</b></a></p> + +<p>"A client of mine," said a lawyer, "was on the point of death when his +wife was about to present him with a child. I drew up his will, in +which he settled two-thirds of his estate upon his son (if it should +happen to be a boy) and one-third on the mother. But if the child +should be a girl, then two-thirds of the estate should go to the +mother and one-third to the daughter. As a matter of fact, after his +death twins were born—a boy and a girl. A very nice point then arose. +How was the estate to be equitably divided among the three in the +closest possible accordance with the spirit of the dead man's will?"</p> + +<hr style="width: 30%;" /> +<p><a name="X_124_A_QUESTION_OF_DEFINITION" id="X_124_A_QUESTION_OF_DEFINITION"></a><a href="#X_124_A_QUESTION_OF_DEFINITIONa"><b>124.—A QUESTION OF DEFINITION.</b></a></p> + +<p>"My property is exactly a mile square," said one landowner to another.</p> + +<p>"Curiously enough, mine is a square mile," was the reply.</p> + +<p>"Then there is no difference?"</p> + +<p>Is this last statement correct?</p> + +<hr style="width: 30%;" /> +<p><a name="X_125_THE_MINERS_HOLIDAY" id="X_125_THE_MINERS_HOLIDAY"></a><a href="#X_125_THE_MINERS_HOLIDAYa"><b>125.—THE MINERS' HOLIDAY.</b></a></p> + +<p>Seven coal-miners took a holiday at the seaside during a big strike. +Six of the party spent exactly half a sovereign each, but Bill Harris +was more extravagant. Bill spent three shillings more than the average +of the party. What was the actual amount of Bill's expenditure?</p> + +<hr style="width: 30%;" /> +<p><a name="X_126_SIMPLE_MULTIPLICATION" id="X_126_SIMPLE_MULTIPLICATION"></a><a href="#X_126_SIMPLE_MULTIPLICATIONa"><b>126.—SIMPLE MULTIPLICATION.</b></a></p> + +<p>If we number six cards 1, 2, 4, 5, 7, and 8, and arrange them on the +table in this order:—</p> + +<p> +<span style="margin-left: 2em;">1 4 2 8 + 5 7</span><br /> +</p> + +<p>We can demonstrate that in order to multiply by 3 all that is +necessary is to remove the 1 to the other end of the row, and the +thing is done. The answer is 428571. Can you find a number that, when +multiplied by 3 and divided by 2, the answer will be the same as if we +removed the first card (which in this case is to be a 3) From the +beginning of the row to the end?</p> + +<hr style="width: 30%;" /> +<p><a name="X_127_SIMPLE_DIVISION" id="X_127_SIMPLE_DIVISION"></a><a href="#X_127_SIMPLE_DIVISIONa"><b>127.—SIMPLE DIVISION.</b></a></p> + +<p>Sometimes a very simple question in elementary arithmetic will cause a +good deal of perplexity. For example, I want to divide the four +numbers, 701, 1,059, 1,417, and 2,312, by the largest number possible +that will leave the same remainder in every case. How am I to set to +work Of course, by a laborious system of trial one can in time +discover the answer, but there is quite a simple method of doing it if +you can only find it.</p> + +<hr style="width: 30%;" /> +<p><a name="X_128_A_PROBLEM_IN_SQUARES" id="X_128_A_PROBLEM_IN_SQUARES"></a><a href="#X_128_A_PROBLEM_IN_SQUARESa"><b>128.—A PROBLEM IN SQUARES.</b></a></p> + +<p>We possess three square boards. The surface of the first contains five +square feet more than the second, and the second contains five square +feet more than the third. Can you give exact measurements for the +sides of the boards? If you can solve this little puzzle, then try to +find three squares in arithmetical progression, with a common +difference of 7 and also of 13.</p> + +<hr style="width: 30%;" /> +<p><a name="X_129_THE_BATTLE_OF_HASTINGS" id="X_129_THE_BATTLE_OF_HASTINGS"></a><a href="#X_129_THE_BATTLE_OF_HASTINGSa"><b>129.—THE BATTLE OF HASTINGS.</b></a></p> + +<p>All historians know that there is a great deal of mystery and +uncertainty concerning the details of the ever-memorable battle on +that fatal day, October 14, 1066. My puzzle deals with a curious +passage in an ancient monkish chronicle that may never receive the +attention that it deserves, and if I am unable to vouch for the +authenticity of the document it will none the less serve to furnish us +with a problem that can hardly fail to interest those of my readers +who have arithmetical predilections. Here is the passage in question.</p> + +<p>"The men of Harold stood well together, as their wont was, and formed +sixty and one squares, with a like number of men in every square +thereof, and woe to the hardy Norman who ventured to enter their +redoubts; for a single blow of a Saxon war-hatchet would break his +lance and cut through his coat of mail.... When Harold threw himself +into the fray the Saxons were one mighty square of men, shouting the +battle-cries, 'Ut!' 'Olicrosse!' 'Godemitè!'"</p> + +<p>Now, I find that all the contemporary authorities agree that the +Saxons did actually fight in this solid order. For example, in the +"Carmen de Bello Hastingensi," a poem attributed to Guy, Bishop of +Amiens, living at the time of the battle, we are told that "the Saxons +stood fixed in a dense mass," and Henry of Huntingdon records that +"they were like unto a castle, impenetrable to the Normans;" while +Robert Wace, a century after, tells us the same thing. So in this +respect my newly-discovered chronicle may not be greatly in error. But +I have reason to believe that there is something wrong with the actual +figures. Let the reader see what he can make of them.</p> + +<p>The number of men would be sixty-one times a square number; but when +Harold himself joined in the fray they were then able to form one +large square. What is the smallest possible number of men there could +have been?</p> + +<p>In order to make clear to the reader the simplicity of the question, I +will give the lowest solutions in the case of 60 and 62, the numbers +immediately preceding and following 61. They are 60 × 4<sup>2</sup> + 1 = +31<sup>2</sup>, and 62 × 8<sup>2</sup> + 1 = 63<sup>2</sup>. That is, 60 squares of 16 men +each would be 960 men, and when Harold joined them they would be 961 +in number, and so form a square with 31 men on every side. Similarly +in the case of the figures I have given for 62. Now, find the lowest +answer for 61.</p> + +<hr style="width: 30%;" /> +<p><a name="X_130_THE_SCULPTORS_PROBLEM" id="X_130_THE_SCULPTORS_PROBLEM"></a><a href="#X_130_THE_SCULPTORS_PROBLEMa"><b>130.—THE SCULPTOR'S PROBLEM.</b></a></p> + +<p>An ancient sculptor was commissioned to supply two statues, each on a +cubical pedestal. It is with these pedestals that we are concerned. +They were of unequal sizes, as will be seen in the illustration, and +when the time arrived for <span class='pagenum'>Pg 24<a name="Page_24" id="Page_24"></a></span>payment a dispute arose as to whether the +agreement was based on lineal or cubical measurement. But as soon as +they came to measure the two pedestals the matter was at once settled, +because, curiously enough, the number of lineal feet was exactly the +same as the number of cubical feet. The puzzle is to find the +dimensions for two pedestals having this peculiarity, in the smallest +possible figures. You see, if the two pedestals, for example, measure +respectively 3 ft. and 1 ft. on every side, then the lineal +measurement would be 4 ft. and the cubical contents 28 ft., which are +not the same, so these measurements will not do.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q130.png" width="400" height="405" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_131_THE_SPANISH_MISER" id="X_131_THE_SPANISH_MISER"></a><a href="#X_131_THE_SPANISH_MISERa"><b>131.—THE SPANISH MISER.</b></a></p> + +<p>There once lived in a small town in New Castile a noted miser named +Don Manuel Rodriguez. His love of money was only equalled by a strong +passion for arithmetical problems. These puzzles usually dealt in some +way or other with his accumulated treasure, and were propounded by him +solely in order that he might have the pleasure of solving them +himself. Unfortunately very few of them have survived, and when +travelling through Spain, collecting material for a proposed work on +"The Spanish Onion as a Cause of National Decadence," I only +discovered a very few. One of these concerns the three boxes that +appear in the accompanying authentic portrait.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q131.png" width="400" height="472" alt="" title="" /> +</div> + +<p>Each box contained a different number of golden doubloons. The +difference between the number of doubloons in the upper box and the +number in the middle box was the same as the difference between the +number in the middle box and the number in the bottom box. And if the +contents of any two of the boxes were united they would form a square +number. What is the smallest number of doubloons that there could have +been in any one of the boxes?</p> + +<hr style="width: 30%;" /> +<p><a name="X_132_THE_NINE_TREASURE_BOXES" id="X_132_THE_NINE_TREASURE_BOXES"></a><a href="#X_132_THE_NINE_TREASURE_BOXESa"><b>132.—THE NINE TREASURE BOXES.</b></a></p> + +<p>The following puzzle will illustrate the importance on occasions of +being able to fix the minimum and maximum limits of a required number. +This can very frequently be done. For example, it has not yet been +ascertained in how many different ways the knight's tour can be +performed on the chess board; but we know that it is fewer than the +number of combinations of 168 things taken 63 at a time and is greater +than 31,054,144—for the latter is the number of routes of a +particular type. Or, to take a more familiar case, if you ask a man +how many coins he has in his pocket, he may tell you that he has not +the slightest idea. But on further questioning you will get out of him +some such statement as the following: "Yes, I am positive that I have +more than three coins, and equally certain that there are not so many +as twenty-five." Now, the knowledge that a certain number lies between +2 and 12 in my puzzle will enable the solver to find the exact answer; +without that information there would be an infinite number of answers, +from which it would be impossible to select the correct one.</p> + +<p>This is another puzzle received from my friend Don Manuel Rodriguez, +the cranky miser of New Castile. On New Year's Eve in 1879 he showed +me nine treasure boxes, and after informing me that every box +contained a square number of golden doubloons, and that the difference +between the contents of A and B was the same as between B and C, D and +E, E and F, G and H, or H and I, he requested me to tell him the +number of coins in every one of the boxes. At first I thought this was +impossible, as there would be an infinite number of different answers, +but on consideration I found that this was not the case. I discovered +that while every box contained coins, the contents of A, B, C +in<span class='pagenum'>Pg 25<a name="Page_25" id="Page_25"></a></span>creased in weight in alphabetical order; so did D, E, F; and so +did G, H, I; but D or E need not be heavier than C, nor G or H heavier +than F. It was also perfectly certain that box A could not contain +more than a dozen coins at the outside; there might not be half that +number, but I was positive that there were not more than twelve. With +this knowledge I was able to arrive at the correct answer.</p> + +<p>In short, we have to discover nine square numbers such that A, B, C; +and D, E, F; and G, H, I are three groups in arithmetical progression, +the common difference being the same in each group, and A being less +than 12. How many doubloons were there in every one of the nine boxes?</p> + +<hr style="width: 30%;" /> +<p><a name="X_133_THE_FIVE_BRIGANDS" id="X_133_THE_FIVE_BRIGANDS"></a><a href="#X_133_THE_FIVE_BRIGANDSa"><b>133.—THE FIVE BRIGANDS.</b></a></p> + +<p>The five Spanish brigands, Alfonso, Benito, Carlos, Diego, and +Esteban, were counting their spoils after a raid, when it was found +that they had captured altogether exactly 200 doubloons. One of the +band pointed out that if Alfonso had twelve times as much, Benito +three times as much, Carlos the same amount, Diego half as much, and +Esteban one-third as much, they would still have altogether just 200 +doubloons. How many doubloons had each?</p> + +<p>There are a good many equally correct answers to this question. Here +is one of them:</p> + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="0" summary=""> +<tr><td align='left'>A</td><td align='right'>6</td><td align='center'>×</td><td align='right'>12</td><td align='center'>=</td><td align='right'>72</td></tr> +<tr><td align='left'>B</td><td align='right'>12</td><td align='center'>×</td><td align='right'>3</td><td align='center'>=</td><td align='right'>36</td></tr> +<tr><td align='left'>C</td><td align='right'>17</td><td align='center'>×</td><td align='right'>1</td><td align='center'>=</td><td align='right'>17</td></tr> +<tr><td align='left'>D</td><td align='right'>120</td><td align='center'>×</td><td align='right'>½</td><td align='center'>=</td><td align='right'>60</td></tr> +<tr><td align='left'>E</td><td class='bb' align='right'>45</td><td align='center'>×</td><td align='right'><sup>1</sup>/<sub>3</sub></td><td align='center'>=</td><td class='bb' align='right'>15</td></tr> +<tr><td> </td><td align='right'>200</td><td> </td><td> </td><td> </td><td align='center'>200</td></tr> +</table></div> + +<p>The puzzle is to discover exactly how many different answers there +are, it being understood that every man had something and that there +is to be no fractional money—only doubloons in every case.</p> + +<p>This problem, worded somewhat differently, was propounded by Tartaglia +(died 1559), and he flattered himself that he had found one solution; +but a French mathematician of note (M.A. Labosne), in a recent work, +says that his readers will be astonished when he assures them that +there are 6,639 different correct answers to the question. Is this so? +How many answers are there?</p> + +<hr style="width: 30%;" /> +<p><a name="X_134_THE_BANKERS_PUZZLE" id="X_134_THE_BANKERS_PUZZLE"></a><a href="#X_134_THE_BANKERS_PUZZLEa"><b>134.—THE BANKER'S PUZZLE.</b></a></p> + +<p>A banker had a sporting customer who was always anxious to wager on +anything. Hoping to cure him of his bad habit, he proposed as a wager +that the customer would not be able to divide up the contents of a box +containing only sixpences into an exact number of equal piles of +sixpences. The banker was first to put in one or more sixpences (as +many as he liked); then the customer was to put in one or more (but in +his case not more than a pound in value), neither knowing what the +other put in. Lastly, the customer was to transfer from the banker's +counter to the box as many sixpences as the banker desired him to put +in. The puzzle is to find how many sixpences the banker should first +put in and how many he should ask the customer to transfer, so that he +may have the best chance of winning.</p> + +<hr style="width: 30%;" /> +<p><a name="X_135_THE_STONEMASONS_PROBLEM" id="X_135_THE_STONEMASONS_PROBLEM"></a><a href="#X_135_THE_STONEMASONS_PROBLEMa"><b>135.—THE STONEMASON'S PROBLEM.</b></a></p> + +<p>A stonemason once had a large number of cubic blocks of stone in his +yard, all of exactly the same size. He had some very fanciful little +ways, and one of his queer notions was to keep these blocks piled in +cubical heaps, no two heaps containing the same number of blocks. He +had discovered for himself (a fact that is well known to +mathematicians) that if he took all the blocks contained in any number +of heaps in regular order, beginning with the single cube, he could +always arrange those on the ground so as to form a perfect square. +This will be clear to the reader, because one block is a square, 1 + 8 += 9 is a square, 1 + 8 + 27 = 36 is a square, 1 + 8 + 27 + 64 = 100 is +a square, and so on. In fact, the sum of any number of consecutive +cubes, beginning always with 1, is in every case a square number.</p> + +<p>One day a gentleman entered the mason's yard and offered him a certain +price if he would supply him with a consecutive number of these +cubical heaps which should contain altogether a number of blocks that +could be laid out to form a square, but the buyer insisted on more +than three heaps and <i>declined to take the single block</i> because it +contained a flaw. What was the smallest possible number of blocks of +stone that the mason had to supply?</p> + +<hr style="width: 30%;" /> +<p><a name="X_136_THE_SULTANS_ARMY" id="X_136_THE_SULTANS_ARMY"></a><a href="#X_136_THE_SULTANS_ARMYa"><b>136.—THE SULTAN'S ARMY.</b></a></p> + +<p>A certain Sultan wished to send into battle an army that could be +formed into two perfect squares in twelve different ways. What is the +smallest number of men of which that army could be composed? To make +it clear to the novice, I will explain that if there were 130 men, +they could be formed into two squares in only two different ways—81 +and 49, or 121 and 9. Of course, all the men must be used on every +occasion.</p> + +<hr style="width: 30%;" /> +<p><a name="X_137_A_STUDY_IN_THRIFT" id="X_137_A_STUDY_IN_THRIFT"></a><a href="#X_137_A_STUDY_IN_THRIFTa"><b>137.—A STUDY IN THRIFT.</b></a></p> + +<p>Certain numbers are called triangular, because if they are taken to +represent counters or coins they may be laid out on the table so as to +form triangles. The number 1 is always regarded as triangular, just as +1 is a square and a cube number. Place one counter on the table—that +is, the first triangular number. Now place two more counters beneath +it, and you have a triangle of three counters; therefore 3 is +triangular. Next place a row of three more counters, and you have a +triangle of six counters; therefore 6 is triangular. We see that every +row of counters that we add, containing just one more counter than the +row above it, makes a larger triangle.</p> + +<p><span class='pagenum'>Pg 26<a name="Page_26" id="Page_26"></a></span>Now, half the sum of any number and its square is always a triangular +number. Thus half of 2 + 2<sup>2</sup> = 3; half of 3 + 3<sup>2</sup> = 6; half of 4 + +4<sup>2</sup> = 10; half of 5 + 5<sup>2</sup>= 15; and so on. So if we want to form a +triangle with 8 counters on each side we shall require half of 8 + +8<sup>2</sup>, or 36 counters. This is a pretty little property of numbers. +Before going further, I will here say that if the reader refers to the +"Stonemason's Problem" (No. 135) he will remember that the sum of any +number of consecutive cubes beginning with 1 is always a square, and +these form the series 1<sup>2</sup>, 3<sup>2</sup>, 6<sup>2</sup>, 10<sup>2</sup>, etc. It will now be +understood when I say that one of the keys to the puzzle was the fact +that these are always the squares of triangular numbers—that is, the +squares of 1, 3, 6, 10, 15, 21, 28, etc., any of which numbers we have +seen will form a triangle.</p> + +<p>Every whole number is either triangular, or the sum of two triangular +numbers or the sum of three triangular numbers. That is, if we take +any number we choose we can always form one, two, or three triangles +with them. The number 1 will obviously, and uniquely, only form one +triangle; some numbers will only form two triangles (as 2, 4, 11, +etc.); some numbers will only form three triangles (as 5, 8, 14, +etc.). Then, again, some numbers will form both one and two triangles +(as 6), others both one and three triangles (as 3 and 10), others both +two and three triangles (as 7 and 9), while some numbers (like 21) +will form one, two, or three triangles, as we desire. Now for a little +puzzle in triangular numbers.</p> + +<p>Sandy McAllister, of Aberdeen, practised strict domestic economy, and +was anxious to train his good wife in his own habits of thrift. He +told her last New Year's Eve that when she had saved so many +sovereigns that she could lay them all out on the table so as to form +a perfect square, or a perfect triangle, or two triangles, or three +triangles, just as he might choose to ask he would add five pounds to +her treasure. Soon she went to her husband with a little bag of £36 in +sovereigns and claimed her reward. It will be found that the +thirty-six coins will form a square (with side 6), that they will form +a single triangle (with side 8), that they will form two triangles +(with sides 5 and 6), and that they will form three triangles (with +sides 3, 5, and 5). In each of the four cases all the thirty-six coins +are used, as required, and Sandy therefore made his wife the promised +present like an honest man.</p> + +<p>The Scotsman then undertook to extend his promise for five more years, +so that if next year the increased number of sovereigns that she has +saved can be laid out in the same four different ways she will receive +a second present; if she succeeds in the following year she will get a +third present, and so on until she has earned six presents in all. +Now, how many sovereigns must she put together before she can win the +sixth present?</p> + +<p>What you have to do is to find five numbers, the smallest possible, +higher than 36, that can be displayed in the four ways—to form a +square, to form a triangle, to form two triangles, and to form three +triangles. The highest of your five numbers will be your answer.</p> + +<hr style="width: 30%;" /> +<p><a name="X_138_THE_ARTILLERYMENS_DILEMMA" id="X_138_THE_ARTILLERYMENS_DILEMMA"></a><a href="#X_138_THE_ARTILLERYMENS_DILEMMAa"><b>138.—THE ARTILLERYMEN'S DILEMMA.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q138.png" width="400" height="346" alt="" title="" /> +</div> + + +<p>"All cannon-balls are to be piled in square pyramids," was the order +issued to the regiment. This was done. Then came the further order, +"All pyramids are to contain a square number of balls." Whereupon the +trouble arose. "It can't be done," said the major. "Look at this +pyramid, for example; there are sixteen balls at the base, then nine, +then four, then one at the top, making thirty balls in all. But there +must be six more balls, or five fewer, to make a square number." "It +<i>must</i> be done," insisted the general. "All you have to do is to put +the right number of balls in your pyramids." "I've got it!" said a +lieutenant, the mathematical genius of the regiment. "Lay the balls +out singly." "Bosh!" exclaimed the general. "You can't <i>pile</i> one +ball into a pyramid!" Is it really possible to obey both orders?</p> + +<hr style="width: 30%;" /> +<p><a name="X_139_THE_DUTCHMENS_WIVES" id="X_139_THE_DUTCHMENS_WIVES"></a><a href="#X_139_THE_DUTCHMENS_WIVESa"><b>139.—THE DUTCHMEN'S WIVES.</b></a></p> + +<p>I wonder how many of my readers are acquainted with the puzzle of the +"Dutchmen's Wives"—in which you have to determine the names of three +men's wives, or, rather, which wife belongs to each husband. Some +thirty years ago it was "going the rounds," as something quite new, +but I recently discovered it in the <i>Ladies' Diary</i> for 1739-40, so it +was clearly familiar to the fair sex over one hundred and seventy +years ago. How many of our mothers, wives, sisters, daughters, and +aunts could solve the puzzle to-day? A far greater proportion than +then, let us hope.</p> + +<p>Three Dutchmen, named Hendrick, Elas, and Cornelius, and their wives, +Gurtrün, Katrün, and Anna, purchase hogs. Each buys as many as he (or +she) gives shillings for one. Each husband pays altogether three +guineas more than his wife. Hendrick buys twenty-three more hogs than +Katrün, and Elas eleven more <span class='pagenum'>Pg 27<a name="Page_27" id="Page_27"></a></span>than Gurtrün. Now, what was the name of +each man's wife?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q139.png" width="400" height="365" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_140_FIND_ADAS_SURNAME" id="X_140_FIND_ADAS_SURNAME"></a><a href="#X_140_FIND_ADAS_SURNAMEa"><b>140.—FIND ADA'S SURNAME.</b></a></p> + +<p>This puzzle closely resembles the last one, my remarks on the solution +of which the reader may like to apply in another case. It was recently +submitted to a Sydney evening newspaper that indulges in "intellect +sharpeners," but was rejected with the remark that it is childish and +that they only published problems capable of solution! Five ladies, +accompanied by their daughters, bought cloth at the same shop. Each of +the ten paid as many farthings per foot as she bought feet, and each +mother spent 8<i>s</i>. 5¼d. more than her daughter. Mrs. Robinson spent 6<i>s</i>. +more than Mrs. Evans, who spent about a quarter as much as Mrs. Jones. +Mrs. Smith spent most of all. Mrs. Brown bought 21 yards more than +Bessie—one of the girls. Annie bought 16 yards more than Mary and +spent £3, 0<i>s</i>. 8<i>d</i>. more than Emily. The Christian name of the other +girl was Ada. Now, what was her surname?</p> + +<hr style="width: 30%;" /> +<p><a name="X_141_SATURDAY_MARKETING" id="X_141_SATURDAY_MARKETING"></a><a href="#X_141_SATURDAY_MARKETINGa"><b>141.—SATURDAY MARKETING.</b></a></p> + +<p>Here is an amusing little case of marketing which, although it deals +with a good many items of money, leads up to a question of a totally +different character. Four married couples went into their village on a +recent Saturday night to do a little marketing. They had to be very +economical, for among them they only possessed forty shilling coins. +The fact is, Ann spent 1<i>s</i>., Mary spent 2<i>s</i>., Jane spent 3<i>s</i>., and Kate +spent 4<i>s</i>. The men were rather more extravagant than their wives, for +Ned Smith spent as much as his wife, Tom Brown twice as much as his +wife, Bill Jones three times as much as his wife, and Jack Robinson +four times as much as his wife. On the way home somebody suggested +that they should divide what coin they had left equally among them. +This was done, and the puzzling question is simply this: What was the +surname of each woman? Can you pair off the four couples?</p> + + + +<hr style="width: 65%;" /> +<h2><a name="GEOMETRICAL_PROBLEMS" id="GEOMETRICAL_PROBLEMS"></a><a href="#CONTENTS">GEOMETRICAL PROBLEMS.</a></h2> + +<p class='center'> +<span style="margin-left: 0em;">"God geometrizes continually."<br /></span> +<span style="margin-left: 8em;">PLATO.<br /></span> +</p> + +<p>"There is no study," said Augustus de Morgan, "which presents so +simple a beginning as that of geometry; there is none in which +difficulties grow more rapidly as we proceed." This will be found when +the reader comes to consider the following puzzles, though they are +not arranged in strict order of difficulty. And the fact that they +have interested and given pleasure to man for untold ages is no doubt +due in some measure to the appeal they make to the eye as well as to +the brain. Sometimes an algebraical formula or theorem seems to give +pleasure to the mathematician's eye, but it is probably only an +intellectual pleasure. But there can be no doubt that in the case of +certain geometrical problems, notably dissection or superposition +puzzles, the æsthetic faculty in man contributes to the delight. For +example, there are probably few readers who will examine the various +cuttings of the Greek cross in the following pages without being in +some degree stirred by a sense of beauty. Law and order in Nature are +always pleasing to contemplate, but when they come under the very eye +they seem to make a specially strong appeal. Even the person with no +geometrical knowledge whatever is induced after the inspection of such +things to exclaim, "How very pretty!" In fact, I have known more than +one person led on to a study of geometry by the fascination of +cutting-out puzzles. I have, therefore, thought it well to keep these +dissection puzzles distinct from the geometrical problems on more +general lines.</p> + + +<h2><a name="DISSECTION_PUZZLES" id="DISSECTION_PUZZLES"></a><a href="#CONTENTS">DISSECTION PUZZLES.</a></h2> + + +<p class='center'> +"Take him and cut him out in little stars."<br /> +<span style="margin-left: 8em;"><i>Romeo and Juliet</i>, iii. 2.<br /></span> +</p> + +<p>Puzzles have infinite variety, but perhaps there is no class more +ancient than dissection, cutting-out, or superposition puzzles. They +were certainly known to the Chinese several thousand years before the +Christian era. And they are just as fascinating to-day as they can +have been at any period of their history. It is supposed by those who +have investigated the matter that the ancient Chinese philosophers +used these <span class='pagenum'>Pg 28<a name="Page_28" id="Page_28"></a></span>puzzles as a sort of kindergarten method of imparting the +principles of geometry. Whether this was so or not, it is certain that +all good dissection puzzles (for the nursery type of jig-saw puzzle, +which merely consists in cutting up a picture into pieces to be put +together again, is not worthy of serious consideration) are really +based on geometrical laws. This statement need not, however, frighten +off the novice, for it means little more than this, that geometry will +give us the "reason why," if we are interested in knowing it, though +the solutions may often be discovered by any intelligent person after +the exercise of patience, ingenuity, and common sagacity.</p> + +<p>If we want to cut one plane figure into parts that by readjustment +will form another figure, the first thing is to find a way of doing it +at all, and then to discover how to do it in the fewest possible +pieces. Often a dissection problem is quite easy apart from this +limitation of pieces. At the time of the publication in the <i>Weekly +Dispatch</i>, in 1902, of a method of cutting an equilateral triangle +into four parts that will form a square (see No. 26, "Canterbury +Puzzles"), no geometrician would have had any difficulty in doing what +is required in five pieces: the whole point of the discovery lay in +performing the little feat in four pieces only.</p> + +<p>Mere approximations in the case of these problems are valueless; the +solution must be geometrically exact, or it is not a solution at all. +Fallacies are cropping up now and again, and I shall have occasion to +refer to one or two of these. They are interesting merely as +fallacies. But I want to say something on two little points that are +always arising in cutting-out puzzles—the questions of "hanging by a +thread" and "turning over." These points can best be illustrated by a +puzzle that is frequently to be found in the old books, but invariably +with a false solution. The puzzle is to cut the figure shown in Fig. 1 +into three pieces that will fit together and form a half-square +triangle. The answer that is invariably given is that shown in Figs. 1 +and 2. Now, it is claimed that the four pieces marked C are really +only one piece, because they may be so cut that they are left "hanging +together by a mere thread." But no serious puzzle lover will ever +admit this. If the cut is made so as to leave the four pieces joined +in one, then it cannot result in a perfectly exact solution. If, on +the other hand, the solution is to be exact, then there will be four +pieces—or six pieces in all. It is, therefore, not a solution in +three pieces.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectiona.png" width="400" height="215" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionb.png" width="400" height="222" alt="" title="" /> +</div> + +<p>If, however, the reader will look at the solution in Figs. 3 and 4, he +will see that no such fault can be found with it. There is no question +whatever that there are three pieces, and the solution is in this +respect quite satisfactory. But another question arises. It will be +found on inspection that the piece marked F, in Fig. 3, is turned over +in Fig. 4—that is to say, a different side has necessarily to be +presented. If the puzzle were merely to be cut out of cardboard or +wood, there might be no objection to this reversal, but it is quite +possible that the material would not admit of being reversed. There +might be a pattern, a polish, a difference of texture, that prevents +it. But it is generally understood that in dissection puzzles you are +allowed to turn pieces over unless it is distinctly stated that you +may not do so. And very often a puzzle is greatly improved by the +added condition, "no piece may be turned over." I have often made +puzzles, too, in which the diagram has a small repeated pattern, and +the pieces have then so to be cut that not only is there no turning +over, but the pattern has to be matched, which cannot be done if the +pieces are turned round, even with the proper side uppermost.</p> + +<p>Before presenting a varied series of cutting-out puzzles, some very +easy and others difficult, I propose to consider one family +alone—those problems involving what is known as the Greek cross with +the square. This will exhibit a great variety of curious +transpositions, and, by having the solutions as we go along, the +reader will be saved the trouble of perpetually turning to another +part of the book, and will have everything under his eye. It is hoped +that in this way the article may prove somewhat instructive to the +novice and interesting to others.</p> + + +<h2><a name="GREEK_CROSS_PUZZLES" id="GREEK_CROSS_PUZZLES"></a><a href="#CONTENTS">GREEK CROSS PUZZLES.</a></h2> + +<p class='center'> +"To fret thy soul with crosses."<br /> +<span style="margin-left: 8em;">SPENSER.<br /></span> +</p> + +<p class='center'> +"But, for my part, it was Greek to me."<br /> +<span style="margin-left: 8em;"><i>Julius Cæsar</i>, i. 2.<br /></span> +</p> + +<p>Many people are accustomed to consider the cross as a wholly Christian +symbol. This is erroneous: it is of very great antiquity. The ancient +Egyptians employed it as a sacred <span class='pagenum'>Pg 29<a name="Page_29" id="Page_29"></a></span>symbol, and on Greek sculptures we +find representations of a cake (the supposed real origin of our hot +cross buns) bearing a cross. Two such cakes were discovered at +Herculaneum. Cecrops offered to Jupiter Olympus a sacred cake or +<i>boun</i> of this kind. The cross and ball, so frequently found on +Egyptian figures, is a circle and the <i>tau</i> cross. The circle +signified the eternal preserver of the world, and the T, named from +the Greek letter <i>tau</i>, is the monogram of Thoth, the Egyptian +Mercury, meaning wisdom. This <i>tau</i> cross is also called by Christians +the cross of St. Anthony, and is borne on a badge in the bishop's +palace at Exeter. As for the Greek or mundane cross, the cross with +four equal arms, we are told by competent antiquaries that it was +regarded by ancient occultists for thousands of years as a sign of the +dual forces of Nature—the male and female spirit of everything that +was everlasting.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionfig5.png" width="400" height="370" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionc.png" width="400" height="238" alt="" title="" /> +</div> + +<p>The Greek cross, as shown in Fig. 5, is formed by the assembling +together of five equal squares. We will start with what is known as +the Hindu problem, supposed to be upwards of three thousand years old. +It appears in the seal of Harvard College, and is often given in old +works as symbolical of mathematical science and exactitude. Cut the +cross into five pieces to form a square. Figs. 6 and 7 show how this +is done. It was not until the middle of the nineteenth century that we +found that the cross might be transformed into a square in only four +pieces. Figs. 8 and 9 will show how to do it, if we further require +the four pieces to be all of the same size and shape. This Fig. 9 is +remarkable because, according to Dr. Le Plongeon and others, as +expounded in a work by Professor Wilson of the Smithsonian Institute, +here we have the great Swastika, or sign, of "good luck to you "—the +most ancient symbol of the human race of which there is any record. +Professor Wilson's work gives some four hundred illustrations of this +curious sign as found in the Aztec mounds of Mexico, the pyramids of +Egypt, the ruins of Troy, and the ancient lore of India and China. One +might almost say there is a curious affinity between the Greek cross +and Swastika! If, however, we require that the four pieces shall be +produced by only two clips of the scissors (assuming the puzzle is in +paper form), then we must cut as in Fig. 10 to form Fig. 11, the first +clip of the scissors being from <i>a</i> to <i>b</i>. Of course folding the +paper, or holding the pieces together after the first cut, would not +in this case be allowed. But there is an infinite number of different +ways of making the cuts to solve the puzzle in four pieces. To this +point I propose to return.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectiond.png" width="400" height="239" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectione.png" width="400" height="249" alt="" title="" /> +</div> + +<p>It will be seen that every one of these puzzles has its reverse +puzzle—to cut a square into pieces to form a Greek cross. But as a +square has not so many angles as the cross, it is not always equally +easy to discover the true directions of the cuts. Yet in the case of +the examples given, I will leave the reader to determine their +direction for himself, as they are rather obvious from the diagrams.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionf.png" width="400" height="206" alt="" title="" /> +</div> + +<p><span class='pagenum'>Pg 30<a name="Page_30" id="Page_30"></a></span>Cut a square into five pieces that will form two separate Greek +crosses of <i>different sizes</i>. This is quite an easy puzzle. As will be +seen in Fig. 12, we have only to divide our square into 25 little +squares and then cut as shown. The cross A is cut out entire, and the +pieces B, C, D, and E form the larger cross in Fig. 13. The reader may +here like to cut the single piece, B, into four pieces all similar in +shape to itself, and form a cross with them in the manner shown in +Fig. 13. I hardly need give the solution.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectiong.png" width="400" height="216" alt="" title="" /> +</div> + + +<p>Cut a square into five pieces that will form two separate Greek +crosses of exactly the <i>same size</i>. This is more difficult. We make +the cuts as in Fig. 14, where the cross A comes out entire and the +other four pieces form the cross in Fig. 15. The direction of the cuts +is pretty obvious. It will be seen that the sides of the square in +Fig. 14 are marked off into six equal parts. The sides of the cross +are found by ruling lines from certain of these points to others.</p> + + +<p>I will now explain, as I promised, why a Greek cross may be cut into +four pieces in an infinite number of different ways to make a square. +Draw a cross, as in Fig. 16. Then draw on transparent paper the square +shown in Fig. 17, taking care that the distance <i>c</i> to <i>d</i> is exactly +the same as the distance <i>a</i> to <i>b</i> in the cross. Now place the +transparent paper over the cross and slide it about into different +positions, only be very careful always to keep the square at the same +angle to the cross as shown, where <i>a</i> <i>b</i> is parallel to <i>c</i> <i>d</i>. If +you place the point <i>c</i> exactly over <i>a</i> the lines will indicate the +solution (Figs. 10 and 11). If you place <i>c</i> in the very centre of the +dotted square, it will give the solution in Figs. 8 and 9. You will +now see that by sliding the square about so that the point <i>c</i> is +always within the dotted square you may get as many different +solutions as you like; because, since an infinite number of different +points may theoretically be placed within this square, there must be +an infinite number of different solutions. But the point <i>c</i> need not +necessarily be placed within the dotted square. It may be placed, for +example, at point <i>e</i> to give a solution in four pieces. Here the +joins at <i>a</i> and <i>f</i> may be as slender as you like. Yet if you once +get over the edge at <i>a</i> or <i>f</i> you no longer have a solution in four +pieces. This proof will be found both entertaining and instructive. If +you do not happen to have any transparent paper at hand, any thin +paper will of course do if you hold the two sheets against a pane of +glass in the window.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionh.png" width="400" height="279" alt="" title="" /> +</div> + +<p>It may have been noticed from the solutions of the puzzles that I have +given that the side of the square formed from the cross is always +equal to the distance <i>a</i> to <i>b</i> in Fig. 16. This must necessarily be +so, and I will presently try to make the point quite clear.</p> + +<p>We will now go one step further. I have already said that the ideal +solution to a cutting-out puzzle is always that which requires the +fewest possible pieces. We have just seen that two crosses of the same +size may be cut out of a square in five pieces. The reader who +succeeded in solving this perhaps asked himself: "Can it be done in +fewer pieces?" This is just the sort of question that the true puzzle +lover is always asking, and it is the right attitude for him to adopt. +The answer to the question is that the puzzle may be solved in four +pieces—the fewest possible. This, then, is a new puzzle. Cut a square +into four pieces that will form two Greek crosses of the same size.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectioni.png" width="400" height="169" alt="" title="" /> +</div> + +<p>The solution is very beautiful. If you divide by points the sides of +the square into three equal parts, the directions of the lines in Fig. +18 will be quite obvious. If you cut along these lines, <span class='pagenum'>Pg 31<a name="Page_31" id="Page_31"></a></span>the pieces A +and B will form the cross in Fig. 19 and the pieces C and D the +similar cross in Fig. 20. In this square we have another form of +Swastika.</p> + +<p>The reader will here appreciate the truth of my remark to the effect +that it is easier to find the directions of the cuts when transforming +a cross to a square than when converting a square into a cross. Thus, +in Figs. 6, 8, and 10 the directions of the cuts are more obvious than +in Fig. 14, where we had first to divide the sides of the square into +six equal parts, and in Fig. 18, where we divide them into three equal +parts. Then, supposing you were required to cut two equal Greek +crosses, each into two pieces, to form a square, a glance at Figs. 19 +and 20 will show how absurdly more easy this is than the reverse +puzzle of cutting the square to make two crosses.</p> + +<p>Referring to my remarks on "fallacies," I will now give a little +example of these "solutions" that are not solutions. Some years ago a +young correspondent sent me what he evidently thought was a brilliant +new discovery—the transforming of a square into a Greek cross in four +pieces by cuts all parallel to the sides of the square. I give his +attempt in Figs. 21 and 22, where it will be seen that the four pieces +do not form a symmetrical Greek cross, because the four arms are not +really squares but oblongs. To make it a true Greek cross we should +require the additions that I have indicated with dotted lines. Of +course his solution produces a cross, but it is not the symmetrical +Greek variety required by the conditions of the puzzle. My young +friend thought his attempt was "near enough" to be correct; but if he +bought a penny apple with a sixpence he probably would not have +thought it "near enough" if he had been given only fourpence change. +As the reader advances he will realize the importance of this question +of exactitude.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionj.png" width="400" height="251" alt="" title="" /> +</div> +<p>In these cutting-out puzzles it is necessary not only to get the +directions of the cutting lines as correct as possible, but to +remember that these lines have no width. If after cutting up one of +the crosses in a manner indicated in these articles you find that the +pieces do not exactly fit to form a square, you may be certain that +the fault is entirely your own. Either your cross was not exactly +drawn, or your cuts were not made quite in the right directions, or +(if you used wood and a fret-saw) your saw was not sufficiently fine. +If you cut out the puzzles in paper with scissors, or in cardboard +with a penknife, no material is lost; but with a saw, however fine, +there is a certain loss. In the case of most puzzles this slight loss +is not sufficient to be appreciable, if the puzzle is cut out on a +large scale, but there have been instances where I have found it +desirable to draw and cut out each part separately—not from one +diagram—in order to produce a perfect result.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionk.png" width="400" height="213" alt="" title="" /> +</div> + +<p>Now for another puzzle. If you have cut out the five pieces indicated +in Fig. 14, you will find that these can be put together so as to form +the curious cross shown in Fig. 23. So if I asked you to cut Fig. 24 +into five pieces to form either a square or two equal Greek crosses +you would know how to do it. You would make the cuts as in Fig. 23, +and place them together as in Figs. 14 and 15. But I want something +better than that, and it is this. Cut Fig. 24 into only four pieces +that will fit together and form a square.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionl.png" width="400" height="208" alt="" title="" /> +</div> + +<p>The solution to the puzzle is shown in Figs. 25 and 26. The direction +of the cut dividing A and C in the first diagram is very obvious, and +the second cut is made at right angles to it. That the four pieces +should fit together and form a square will surprise the novice, who +will do well to study the puzzle with some care, as it is most +instructive.</p> + +<p>I will now explain the beautiful rule by which we determine the size +of a square that shall have the same area as a Greek cross, for it is +applicable, and necessary, to the solution of almost every dissection +puzzle that we meet with. It was first discovered by the philosopher +Pythagoras, who died 500 B.C., and is the 47th proposition of Euclid. +The young reader who knows nothing of the elements of geometry will +get some idea of the fascinating character of that science. The +triangle ABC in Fig. 27 is what we call a right-angled triangle, +because the side BC is at right angles to the side AB. Now if we build +up a square on each side of the tri<span class='pagenum'>Pg 32<a name="Page_32" id="Page_32"></a></span>angle, the squares on AB and BC +will together be exactly equal to the square on the long side AC, +which we call the hypotenuse. This is proved in the case I have given +by subdividing the three squares into cells of equal dimensions.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionm.png" width="400" height="213" alt="" title="" /> +</div> + +<p>It will be seen that 9 added to 16 equals 25, the number of cells in +the large square. If you make triangles with the sides 5, 12 and 13, +or with 8, 15 and 17, you will get similar arithmetical proofs, for +these are all "rational" right-angled triangles, but the law is +equally true for all cases. Supposing we cut off the lower arm of a +Greek cross and place it to the left of the upper arm, as in Fig. 28, +then the square on EF added to the square on DE exactly equals a +square on DF. Therefore we know that the square of DF will contain the +same area as the cross. This fact we have proved practically by the +solutions of the earlier puzzles of this series. But whatever length +we give to DE and EF, we can never give the exact length of DF in +numbers, because the triangle is not a "rational" one. But the law is +none the less geometrically true.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionn.png" width="400" height="198" alt="" title="" /> +</div> + +<p>Now look at Fig. 29, and you will see an elegant method for cutting a +piece of wood of the shape of two squares (of any relative dimensions) +into three pieces that will fit together and form a single square. If +you mark off the distance <i>ab</i> equal to the side <i>cd</i> the directions +of the cuts are very evident. From what we have just been considering, +you will at once see why <i>bc</i> must be the length of the side of the +new square. Make the experiment as often as you like, taking different +relative proportions for the two squares, and you will find the rule +always come true. If you make the two squares of exactly the same +size, you will see that the diagonal of any square is always the side +of a square that is twice the size. All this, which is so simple that +anybody can understand it, is very essential to the solving of +cutting-out puzzles. It is in fact the key to most of them. And it is +all so beautiful that it seems a pity that it should not be familiar +to everybody.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectiono.png" width="400" height="250" alt="" title="" /> +</div> + +<p>We will now go one step further and deal with the half-square. Take a +square and cut it in half diagonally. Now try to discover how to cut +this triangle into four pieces that will form a Greek cross. The +solution is shown in Figs. 31 and 32. In this case it will be seen +that we divide two of the sides of the triangle into three equal parts +and the long side into four equal parts. Then the direction of the +cuts will be easily found. It is a pretty puzzle, and a little more +difficult than some of the others that I have given. It should be +noted again that it would have been much easier to locate the cuts in +the reverse puzzle of cutting the cross to form a half-square +triangle.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionp.png" width="400" height="230" alt="" title="" /> +</div> + +<p>Another ideal that the puzzle maker always keeps in mind is to +contrive that there shall, if possible, be only one correct solution. +Thus, in the case of the first puzzle, if we only require that a Greek +cross shall be cut into four pieces to form a square, there is, as I +have shown, an infinite number of different solutions. It makes a +better puzzle to add the condition that all the four pieces shall be +of the same size and shape, because it can then be solved in only one +way, as in Figs. 8 and 9. In this way, too, a puzzle that is too easy +to be interesting may be improved by such an addition. Let us take an +example. We have seen in Fig. 28 that Fig. 33 can be cut into two +pieces to form a Greek cross. I suppose an intelligent child would do +it in five minutes. But suppose we say that the puzzle has to be +solved with a piece of wood that has <span class='pagenum'>Pg 33<a name="Page_33" id="Page_33"></a></span>a bad knot in the position shown +in Fig. 33—a knot that we must not attempt to cut through—then a +solution in two pieces is barred out, and it becomes a more +interesting puzzle to solve it in three pieces. I have shown in Figs. +33 and 34 one way of doing this, and it will be found entertaining to +discover other ways of doing it. Of course I could bar out all these +other ways by introducing more knots, and so reduce the puzzle to a +single solution, but it would then be overloaded with conditions.</p> + +<p>And this brings us to another point in seeking the ideal. Do not +overload your conditions, or you will make your puzzle too complex to +be interesting. The simpler the conditions of a puzzle are, the +better. The solution may be as complex and difficult as you like, or +as happens, but the conditions ought to be easily understood, or +people will not attempt a solution.</p> + +<p>If the reader were now asked "to cut a half-square into as few pieces +as possible to form a Greek cross," he would probably produce our +solution, Figs. 31-32, and confidently claim that he had solved the +puzzle correctly. In this way he would be wrong, because it is not now +stated that the square is to be divided diagonally. Although we should +always observe the exact conditions of a puzzle we must not read into +it conditions that are not there. Many puzzles are based entirely on +the tendency that people have to do this.</p> + +<p>The very first essential in solving a puzzle is to be sure that you +understand the exact conditions. Now, if you divided your square in +half so as to produce Fig. 35 it is possible to cut it into as few as +three pieces to form a Greek cross. We thus save a piece.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionq.png" width="400" height="263" alt="" title="" /> +</div> + +<p>I give another puzzle in Fig. 36. The dotted lines are added merely to +show the correct proportions of the figure—a square of 25 cells with +the four corner cells cut out. The puzzle is to cut this figure into +five pieces that will form a Greek cross (entire) and a square.</p> + +<p>The solution to the first of the two puzzles last given—to cut a +rectangle of the shape of a half-square into three pieces that will +form a Greek cross—is shown in Figs. 37 and 38. It will be seen that +we divide the long sides of the oblong into six equal parts and the +short sides into three equal parts, in order to get the points that +will indicate the direction of the cuts. The reader should compare +this solution with some of the previous illustrations. He will see, +for example, that if we continue the cut that divides B and C in the +cross, we get Fig. 15.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionr.png" width="400" height="257" alt="" title="" /> +</div> + +<p>The other puzzle, like the one illustrated in Figs. 12 and 13, will +show how useful a little arithmetic may sometimes prove to be in the +solution of dissection puzzles. There are twenty-one of those little +square cells into which our figure is subdivided, from which we have +to form both a square and a Greek cross. Now, as the cross is built up +of five squares, and 5 from 21 leaves 16—a square number—we ought +easily to be led to the solution shown in Fig. 39. It will be seen +that the cross is cut out entire, while the four remaining pieces form +the square in Fig. 40.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disections.png" width="400" height="211" alt="" title="" /> +</div> + +<p>Of course a half-square rectangle is the same as a double square, or +two equal squares joined together. Therefore, if you want to solve the +puzzle of cutting a Greek cross into four pieces to form two separate +squares of the same size, all you have to do is to continue the short +cut in Fig. 38 right across the cross, and you will have four pieces +of the same size and shape. Now divide Fig. 37 into two equal squares +by a horizontal cut midway and you will see the four pieces forming +the two squares.</p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/disectiont.png" width="300" height="338" alt="" title="" /> +</div> + +<p><span class='pagenum'>Pg 34<a name="Page_34" id="Page_34"></a></span>Cut a Greek cross into five +pieces that will form two separate squares, one of which shall contain +half the area of one of the arms of the cross. In further illustration +of what I have already written, if the two squares of the same size A +B C D and B C F E, in Fig. 41, are cut in the manner indicated by the +dotted lines, the four pieces will form the large square A G E C. We +thus see that the diagonal A C is the side of a square twice the size +of A B C D. It is also clear that half the diagonal of any square is +equal to the side of a square of half the area. Therefore, if the +large square in the diagram is one of the arms of your cross, the +small square is the size of one of the squares required in the +puzzle.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/disectionu.png" width="400" height="237" alt="" title="" /> +</div> + + +<p>The solution is shown in Figs. 42 and 43. It will be seen that the +small square is cut out whole and the large square composed of the +four pieces B, C, D, and E. After what I have written, the reader will +have no difficulty in seeing that the square A is half the size of one +of the arms of the cross, because the length of the diagonal of the +former is clearly the same as the side of the latter. The thing is now +self-evident. I have thus tried to show that some of these puzzles +that many people are apt to regard as quite wonderful and bewildering, +are really not difficult if only we use a little thought and judgment. +In conclusion of this particular subject I will give four Greek cross +puzzles, with detached solutions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_142_THE_SILK_PATCHWORK" id="X_142_THE_SILK_PATCHWORK"></a><a href="#X_142_THE_SILK_PATCHWORKa"><b>142.—THE SILK PATCHWORK.</b></a></p> + +<p>The lady members of the Wilkinson family had made a simple patchwork +quilt, as a small Christmas present, all composed of square pieces of +the same size, as shown in the illustration. It only lacked the four +corner pieces to make it complete. Somebody pointed out to them that +if you unpicked the Greek cross in the middle and then cut the +stitches along the dark joins, the four pieces all of the same size +and shape would fit together and form a square. This the reader knows, +from the solution in Fig. 39, is quite easily done. But George +Wilkinson suddenly suggested to them this poser. He said, "Instead of +picking out the cross entire, and forming the square from four equal +pieces, can you cut out a square entire and four equal pieces that +will form a perfect Greek cross?" The puzzle is, of course, now quite +easy.</p> + +<div class="figcenter" style="width: 550px;"> +<img src="images/q142.png" width="550" height="456" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 35<a name="Page_35" id="Page_35"></a></span><a name="X_143_TWO_CROSSES_FROM_ONE" id="X_143_TWO_CROSSES_FROM_ONE"></a><b><a href="#X_143_TWO_CROSSES_FROM_ONEa">143.—TWO CROSSES FROM ONE.</a></b></p> + +<p>Cut a Greek cross into five pieces that will form two such crosses, +both of the same size. The solution of this puzzle is very beautiful.</p> + +<hr style="width: 30%;" /> +<p><a name="X_144_THE_CROSS_AND_THE_TRIANGLE" id="X_144_THE_CROSS_AND_THE_TRIANGLE"></a><a href="#X_144_THE_CROSS_AND_THE_TRIANGLEa"><b>144.—THE CROSS AND THE TRIANGLE.</b></a></p> + +<p>Cut a Greek cross into six pieces that will form an equilateral +triangle. This is another hard problem, and I will state here that a +solution is practically impossible without a previous knowledge of my +method of transforming an equilateral triangle into a square (see No. +26, "Canterbury Puzzles").</p> + +<hr style="width: 30%;" /> +<p><a name="X_145_THE_FOLDED_CROSS" id="X_145_THE_FOLDED_CROSS"></a><a href="#X_145_THE_FOLDED_CROSSa"><b>145.—THE FOLDED CROSS.</b></a></p> + +<p>Cut out of paper a Greek cross; then so fold it that with a single +straight cut of the scissors the four pieces produced will form a +square.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="VARIOUS_DISSECTION_PUZZLES" id="VARIOUS_DISSECTION_PUZZLES"></a><a href="#CONTENTS">VARIOUS DISSECTION PUZZLES.</a></h2> + + +<p>We will now consider a small miscellaneous selection of cutting-out +puzzles, varying in degrees of difficulty.</p> + +<hr style="width: 30%;" /> +<p><a name="X_146_AN_EASY_DISSECTION_PUZZLE" id="X_146_AN_EASY_DISSECTION_PUZZLE"></a><a href="#X_146_AN_EASY_DISSECTION_PUZZLEa"><b>146.—AN EASY DISSECTION PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q146.png" width="400" height="211" alt="" title="" /> +</div> + +<p>First, cut out a piece of paper or cardboard of the shape shown in the +illustration. It will be seen at once that the proportions are simply +those of a square attached to half of another similar square, divided +diagonally. The puzzle is to cut it into four pieces all of precisely +the same size and shape.</p> + +<hr style="width: 30%;" /> +<p><a name="X_147_AN_EASY_SQUARE_PUZZLE" id="X_147_AN_EASY_SQUARE_PUZZLE"></a><a href="#X_147_AN_EASY_SQUARE_PUZZLEa"><b>147.—AN EASY SQUARE PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q147.png" width="400" height="302" alt="" title="" /> +</div> + +<p>If you take a rectangular piece of cardboard, twice as long as it is +broad, and cut it in half diagonally, you will get two of the pieces +shown in the illustration. The puzzle is with five such pieces of +equal size to form a square. One of the pieces may be cut in two, but +the others must be used intact.</p> + +<hr style="width: 30%;" /> +<p><a name="X_148_THE_BUN_PUZZLE" id="X_148_THE_BUN_PUZZLE"></a><a href="#X_148_THE_BUN_PUZZLEa"><b>148.—THE BUN PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q148.png" width="400" height="167" alt="" title="" /> +</div> + +<p>The three circles represent three buns, and it is simply required to +show how these may be equally divided among four boys. The buns must +be regarded as of equal thickness throughout and of equal thickness to +each other. Of course, they must be cut into as few pieces as +possible. To simplify it I will state the rather surprising fact that +only five pieces are necessary, from which it will be seen that one +boy gets his share in two pieces and the other three receive theirs in +a single piece. I am aware that this statement "gives away" the +puzzle, but it should not destroy its interest to those who like to +discover the "reason why."</p> + +<hr style="width: 30%;" /> +<p><a name="X_149_THE_CHOCOLATE_SQUARES" id="X_149_THE_CHOCOLATE_SQUARES"></a><a href="#X_149_THE_CHOCOLATE_SQUARESa"><b>149.—THE CHOCOLATE SQUARES.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q149.png" width="400" height="390" alt="" title="" /> +</div> + +<p>Here is a slab of chocolate, indented at the dotted lines so that the +twenty squares can be easily separated. Make a copy of the slab in +paper or cardboard and then try to cut it into nine pieces so that +they will form four perfect squares all of exactly the same size.</p> + +<hr style="width: 30%;" /> +<p><a name="X_150_DISSECTING_A_MITRE" id="X_150_DISSECTING_A_MITRE"></a><a href="#X_150_DISSECTING_A_MITREa"><b>150.—DISSECTING A MITRE.</b></a></p> + + +<div class="figcenter" style="width: 500px;"> +<img src="images/q150a.png" width="500" height="402" alt="" title="" /> +</div> + +<p>The figure that is perplexing the carpenter in the illustration +represents a mitre. It will be seen that its proportions are those of +a square with one quarter removed. The puzzle is to cut it into five +pieces that will fit together and form a perfect square. I show an +attempt, published in America, to perform the feat in <span class='pagenum'>Pg 36<a name="Page_36" id="Page_36"></a></span>four pieces, +based on what is known as the "step principle," but it is a fallacy.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q150b.png" width="400" height="398" alt="" title="" /> +</div> + +<p>We are told first to cut oft the pieces 1 and 2 and pack them into the +triangular space marked off by the dotted line, and so form a +rectangle.</p> + +<p>So far, so good. Now, we are directed to apply the old step principle, +as shown, and, by moving down the piece 4 one step, form the required +square. But, unfortunately, it does <i>not</i> produce a square: only an +oblong. Call the three long sides of the mitre 84 in. each. Then, +before cutting the steps, our rectangle in three pieces will be 84×63. +The steps must be 10½ in. in height and 12 in. in breadth. +Therefore, by moving down a step we reduce by 12 in. the side 84 in. +and increase by 10½ in. the side 63 in. Hence our final rectangle +must be 72 in. × 73½ in., which certainly is not a square! The fact +is, the step principle can only be applied to rectangles with sides of +particular relative lengths. For example, if the shorter side in this +case were 61<sup>5</sup>/<sub>7</sub> (instead of 63), then the step method would apply. +For the steps would then be 10<sup>2</sup>/<sub>7</sub> in. in height and 12 in. in +breadth. Note that 61<sup>5</sup>/<sub>7</sub> × 84= the square of 72. At present no +solution has been found in four pieces, and I do not believe one +possible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_151_THE_JOINERS_PROBLEM" id="X_151_THE_JOINERS_PROBLEM"></a><a href="#X_151_THE_JOINERS_PROBLEMa"><b>151.—THE JOINER'S PROBLEM.</b></a></p> + +<p>I have often had occasion to remark on the practical utility of +puzzles, arising out of an application to the ordinary affairs of life +of the little tricks and "wrinkles" that we learn while solving +recreation problems.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q151.png" width="400" height="471" alt="" title="" /> +</div> + +<p>The joiner, in the illustration, wants to cut the piece of wood into +as few pieces as possible to form a square table-top, without any +waste <span class='pagenum'>Pg 37<a name="Page_37" id="Page_37"></a></span>of material. How should he go to work? How many pieces would +you require?</p> + +<hr style="width: 30%;" /> +<p><a name="X_152_ANOTHER_JOINERS_PROBLEM" id="X_152_ANOTHER_JOINERS_PROBLEM"></a><a href="#X_152_ANOTHER_JOINERS_PROBLEMa"><b>152.—ANOTHER JOINER'S PROBLEM.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q152.png" width="400" height="322" alt="" title="" /> +</div> + +<p>A joiner had two pieces of wood of the shapes and relative proportions +shown in the diagram. He wished to cut them into as few pieces as +possible so that they could be fitted together, without waste, to form +a perfectly square table-top. How should he have done it? There is no +necessity to give measurements, for if the smaller piece (which is +half a square) be made a little too large or a little too small it +will not affect the method of solution.</p> + +<hr style="width: 30%;" /> +<p><a name="X_153_A_CUTTING-OUT_PUZZLE" id="X_153_A_CUTTING-OUT_PUZZLE"></a><a href="#X_153_A_CUTTING-OUT_PUZZLEa"><b>153.—A CUTTING-OUT PUZZLE.</b></a></p> + +<p>Here is a little cutting-out poser. I take a strip of paper, measuring +five inches by one inch, and, by cutting it into five pieces, the +parts fit together and form a square, as shown in the illustration. +Now, it is quite an interesting puzzle to discover how we can do this +in only four pieces.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q153.png" width="400" height="131" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_154_MRS_HOBSONS_HEARTHRUG" id="X_154_MRS_HOBSONS_HEARTHRUG"></a><a href="#X_154_MRS_HOBSONS_HEARTHRUGa"><b>154.—MRS. HOBSON'S HEARTHRUG.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q154.png" width="400" height="289" alt="" title="" /> +</div> + +<p>Mrs. Hobson's boy had an accident when playing with the fire, and +burnt two of the corners of a pretty hearthrug. The damaged corners +have been cut away, and it now has the appearance and proportions +shown in my diagram. How is Mrs. Hobson to cut the rug into the fewest +possible pieces that will fit together and form a perfectly square +rug? It will be seen that the rug is in the proportions 36 × 27 (it +does not matter whether we say inches or yards), and each piece cut +away measured 12 and 6 on the outside.</p> + +<hr style="width: 30%;" /> +<p><a name="X_155_THE_PENTAGON_AND_SQUARE" id="X_155_THE_PENTAGON_AND_SQUARE"></a><a href="#X_155_THE_PENTAGON_AND_SQUAREa"><b>155.—THE PENTAGON AND SQUARE.</b></a></p> + +<p>I wonder how many of my readers, amongst those who have not given any +close attention to the elements of geometry, could draw a regular +pentagon, or five-sided figure, if they suddenly required to do so. A +regular hexagon, or six-sided figure, is easy enough, for everybody +knows that all you have to do is to describe a circle and then, taking +the radius as the length of one of the sides, mark off the six points +round the circumference. But a pentagon is quite another matter. So, +as my puzzle has to do with the cutting up of a regular pentagon, it +will perhaps be well if I first show my less experienced readers how +this figure is to be correctly drawn. Describe a circle and draw the +two lines H B and D G, in the diagram, through the centre at right +angles. Now find the point A, midway between C and B. Next place the +point of your compasses at A and with <span class='pagenum'>Pg 38<a name="Page_38" id="Page_38"></a></span>the distance A D describe the +arc cutting H B at E. Then place the point of your compasses at D and +with the distance D E describe the arc cutting the circumference at F. +Now, D F is one of the sides of your pentagon, and you have simply to +mark off the other sides round the circle. Quite simple when you know +how, but otherwise somewhat of a poser.</p> + +<div class="figcenter" style="width: 499px;"> +<img src="images/q155.png" width="499" height="491" alt="" title="" /> +</div> + +<p>Having formed your pentagon, the puzzle is to cut it into the fewest +possible pieces that will fit together and form a perfect square.</p> + +<hr style="width: 30%;" /> +<p><a name="X_156_THE_DISSECTED_TRIANGLE" id="X_156_THE_DISSECTED_TRIANGLE"></a><a href="#X_156_THE_DISSECTED_TRIANGLEa"><b>156.—THE DISSECTED TRIANGLE.</b></a></p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/q156.png" width="500" height="340" alt="" title="" /> +</div> + +<p>A good puzzle is that which the gentleman in the illustration is +showing to his friends. He has simply cut out of paper an equilateral +triangle—that is, a triangle with all its three sides of the same +length. He proposes that it shall be cut into five pieces in such a +way that they will fit together and form either two or three smaller +equilateral triangles, using all the material in each case. Can you +discover how the cuts should be made?</p> + +<p>Remember that when you have made your five pieces, you must be able, +as desired, to put them together to form either the single original +triangle or to form two triangles or to form three triangles—all +equilateral.</p> + +<hr style="width: 30%;" /> +<p><a name="X_157_THE_TABLE-TOP_AND_STOOLS" id="X_157_THE_TABLE-TOP_AND_STOOLS"></a><a href="#X_157_THE_TABLE-TOP_AND_STOOLSa"><b>157.—THE TABLE-TOP AND STOOLS.</b></a></p> + +<p>I have frequently had occasion to show that the published answers to a +great many of the oldest and most widely known puzzles are either +quite incorrect or capable of improvement. I propose to consider the +old poser of the table-top and stools that most of my readers have +probably seen in some form or another in books compiled for the +recreation of childhood.</p> + +<p>The story is told that an economical and ingenious schoolmaster once +wished to convert a circular table-top, for which he had no use, into +seats for two oval stools, each with a hand-hole in the centre. He +instructed the carpenter to make the cuts as in the illustration and +then join the eight pieces together in the manner shown. So impressed +was he with the ingenuity of his performance that he set the puzzle to +his geometry class as a little study in dissection. But the remainder +of the story has never been published, because, so it is said, it was +a characteristic of the principals of academies that they would never +admit that they could err. I get my information from a de<span class='pagenum'>Pg 39<a name="Page_39" id="Page_39"></a></span>scendant of +the original boy who had most reason to be interested in the matter.</p> + +<p>The clever youth suggested modestly to the master that the hand-holes +were too big, and that a small boy might perhaps fall through them. He +therefore proposed another way of making the cuts that would get over +this objection. For his impertinence he received such severe +chastisement that he became convinced that the larger the hand-hole in +the stools the more comfortable might they be.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q157.png" width="600" height="263" alt="" title="" /> +</div> + +<p>Now what was the method the boy proposed?</p> + +<p>Can you show how the circular table-top may be cut into eight pieces +that will fit together and form two oval seats for stools (each of +exactly the same size and shape) and each having similar hand-holes of +smaller dimensions than in the case shown above? Of course, all the +wood must be used.</p> + +<hr style="width: 30%;" /> +<p><a name="X_158_THE_GREAT_MONAD" id="X_158_THE_GREAT_MONAD"></a><a href="#X_158_THE_GREAT_MONADa"><b>158.—THE GREAT MONAD.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q158.png" width="400" height="405" alt="" title="" /> +</div> + +<p>Here is a symbol of tremendous antiquity which is worthy of notice. It +is borne on the Korean ensign and merchant flag, and has been adopted +as a trade sign by the Northern Pacific Railroad Company, though +probably few are aware that it is the Great Monad, as shown in the +sketch below. This sign is to the Chinaman what the cross is to the +Christian. It is the sign of Deity and eternity, while the two parts +into which the circle is divided are called the Yin and the Yan—the +male and female forces of nature. A writer on the subject more than +three thousand years ago is reported to have said in reference to it: +"The illimitable produces the great extreme. The great extreme +produces the two principles. The two principles produce the four +quarters, and from the four quarters we develop the quadrature of the +eight diagrams of Feuh-hi." I hope readers will not ask me to explain +this, for I have not the slightest idea what it means. Yet I am +persuaded that for ages the symbol has had occult and probably +mathematical meanings for the esoteric student.</p> + +<p>I will introduce the Monad in its elementary form. Here are three easy +questions respecting this great symbol:—</p> + +<p>(I.) Which has the greater area, the inner circle containing the Yin +and the Yan, or the outer ring?</p> + +<p>(II.) Divide the Yin and the Yan into four pieces of the same size and +shape by one cut.</p> + +<p>(III.) Divide the Yin and the Yan into four pieces of the same size, +but different shape, by one straight cut.</p> + +<hr style="width: 30%;" /> +<p><a name="X_159_THE_SQUARE_OF_VENEER" id="X_159_THE_SQUARE_OF_VENEER"></a><a href="#X_159_THE_SQUARE_OF_VENEERa"><b>159.—THE SQUARE OF VENEER.</b></a></p> + +<p>The following represents a piece of wood in my possession, 5 in. +square. By markings on the surface it is divided into twenty-five +square inches. I want to discover a way of cutting this piece of wood +into the fewest possible pieces that will fit together and form two +perfect squares of different sizes and of known dimensions. But, +unfortunately, at every one of the sixteen intersections of the cross +lines a small nail has been driven in at some time or other, and my +fret-saw will be injured if it comes in <span class='pagenum'>Pg 40<a name="Page_40" id="Page_40"></a></span>contact with any of these. I +have therefore to find a method of doing the work that will not +necessitate my cutting through any of those sixteen points. How is it +to be done? Remember, the exact dimensions of the two squares must be +given.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q159.png" width="400" height="394" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_160_THE_TWO_HORSESHOES" id="X_160_THE_TWO_HORSESHOES"></a><a href="#X_160_THE_TWO_HORSESHOESa"><b>160.—THE TWO HORSESHOES.</b></a></p> + +<p>Why horseshoes should be considered "lucky" is one of those things +which no man can understand. It is a very old superstition, and John +Aubrey (1626-1700) says, "Most houses at the West End of London have a +horseshoe on the threshold." In Monmouth Street there were seventeen +in 1813 and seven so late as 1855. Even Lord Nelson had one nailed to +the mast of the ship <i>Victory</i>. To-day we find it more conducive to +"good luck" to see that they are securely nailed on the feet of the +horse we are about to drive.</p> + +<p>Nevertheless, so far as the horseshoe, like the Swastika and other +emblems that I have had occasion at times to deal with, has served to +symbolize health, prosperity, and goodwill towards men, we may well +treat it with a certain amount of respectful interest. May there not, +moreover, be some esoteric or lost mathematical mystery concealed in +the form of a horseshoe? I have been looking into this matter, and I +wish to draw my readers' attention to the very remarkable fact that +the pair of horseshoes shown in my illustration are related in a +striking and beautiful manner to the circle, which is the symbol of +eternity. I present this fact in the form of a simple problem, so that +it may be seen how subtly this relation has been concealed for ages +and ages. My readers will, I know, be pleased when they find the key +to the mystery.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q160.png" width="400" height="238" alt="" title="" /> +</div> + +<p>Cut out the two horseshoes carefully round the outline and then cut +them into four pieces, all different in shape, that will fit together +and form a perfect circle. Each shoe must be cut into two pieces and +all the part of the horse's hoof contained within the outline is to be +used and regarded as part of the area.</p> + +<hr style="width: 30%;" /> +<p><a name="X_161_THE_BETSY_ROSS_PUZZLE" id="X_161_THE_BETSY_ROSS_PUZZLE"></a><a href="#X_161_THE_BETSY_ROSS_PUZZLEa"><b>161.—THE BETSY ROSS PUZZLE.</b></a></p> + +<p>A correspondent asked me to supply him with the solution to an old +puzzle that is attributed to a certain Betsy Ross, of Philadelphia, +who showed it to George Washington. It consists in so folding a piece +of paper that with one clip of the scissors a five-pointed star of +Freedom may be produced. Whether the story of the puzzle's origin is a +true one or not I cannot say, but I have a print of the old house in +Philadelphia where the lady is said to have lived, and I believe it +still stands there. But my readers will doubtless be interested in the +little poser.</p> + +<p>Take a circular piece of paper and so fold it that with one cut of the +scissors you can produce a perfect five-pointed star.</p> + +<hr style="width: 30%;" /> +<p><a name="X_162_THE_CARDBOARD_CHAIN" id="X_162_THE_CARDBOARD_CHAIN"></a><a href="#X_162_THE_CARDBOARD_CHAINa"><b>162.—THE CARDBOARD CHAIN.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q162.png" width="400" height="119" alt="" title="" /> +</div> + +<p>Can you cut this chain out of a piece of cardboard without any join +whatever? Every link is solid; without its having been split and +afterwards joined at any place. It is an interesting old puzzle that I +learnt as a child, but I have no knowledge as to its inventor.</p> + +<hr style="width: 30%;" /> +<p><a name="X_163_THE_PAPER_BOX" id="X_163_THE_PAPER_BOX"></a><a href="#X_163_THE_PAPER_BOX"><b>163.—THE PAPER BOX.</b></a></p> + +<p>It may be interesting to introduce here, though it is not strictly a +puzzle, an ingenious method for making a paper box.</p> + +<p>Take a square of stout paper and by successive foldings make all the +creases indicated by the dotted lines in the illustration. Then cut +away the eight little triangular pieces that are shaded, and cut +through the paper along the dark lines. The second illustration shows +the box half folded up, and the reader will have no difficulty in +effecting its completion. Before folding up, the reader might cut out +the circular piece indicated in the diagram, for a purpose I will now +explain.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q163a.png" width="400" height="405" alt="" title="" /> +</div> + +<p>This box will be found to serve excellently for the production of +vortex rings. These rings, <span class='pagenum'>Pg 41<a name="Page_41" id="Page_41"></a></span>which were discussed by Von Helmholtz in +1858, are most interesting, and the box (with the hole cut out) will +produce them to perfection. Fill the box with tobacco smoke by blowing +it gently through the hole. Now, if you hold it horizontally, and +softly tap the side that is opposite to the hole, an immense number of +perfect rings can be produced from one mouthful of smoke. It is best +that there should be no currents of air in the room. People often do +not realise that these rings are formed in the air when no smoke is +used. The smoke only makes them visible. Now, one of these rings, if +properly directed on its course, will travel across the room and put +out the flame of a candle, and this feat is much more striking if you +can manage to do it without the smoke. Of course, with a little +practice, the rings may be blown from the mouth, but the box produces +them in much greater perfection, and no skill whatever is required. +Lord Kelvin propounded the theory that matter may consist of vortex +rings in a fluid that fills all space, and by a development of the +hypothesis he was able to explain chemical combination.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q163b.png" width="400" height="127" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_164_THE_POTATO_PUZZLE" id="X_164_THE_POTATO_PUZZLE"></a><a href="#X_164_THE_POTATO_PUZZLEa"><b>164.—THE POTATO PUZZLE.</b></a></p> + +<p>Take a circular slice of potato, place it on the table, and see into +how large a number of pieces you can divide it with six cuts of a +knife. Of course you must not readjust the pieces or pile them after a +cut. What is the greatest number of pieces you can make?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q164.png" width="400" height="395" alt="" title="" /> +</div> + +<p>The illustration shows how to make sixteen pieces. This can, of +course, be easily beaten.</p> + +<hr style="width: 30%;" /> +<p><a name="X_165_THE_SEVEN_PIGS" id="X_165_THE_SEVEN_PIGS"></a><a href="#X_165_THE_SEVEN_PIGSa"><b>165.—THE SEVEN PIGS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q165.png" width="400" height="410" alt="" title="" /> +</div> + +<p>Here is a little puzzle that was put to one of the sons of Erin the +other day and perplexed him unduly, for it is really quite easy. It +will be seen from the illustration that he was shown a sketch of a +square pen containing seven pigs. He was asked how he would intersect +the pen with three straight fences so as to enclose every pig in a +separate sty. In other words, all you have to do is to take your +pencil and, with three straight strokes across the square, enclose +each pig separately. Nothing could be simpler.</p> + +<p>The Irishman complained that the pigs would not keep still while he +was putting up the fences. He said that they would all flock together, +or one obstinate beast would go into a corner and flock all by +himself. It was pointed out to him that for the purposes of the puzzle +the pigs were stationary. He answered that Irish pigs are not +stationery—they are pork. Being persuaded to make the attempt, he +drew three lines, one of which cut through a pig. When it was +explained that this is not allowed, he protested <span class='pagenum'>Pg 42<a name="Page_42" id="Page_42"></a></span>that a pig was no +use until you cut its throat. "Begorra, if it's bacon ye want without +cutting your pig, it will be all gammon." We will not do the Irishman +the injustice of suggesting that the miserable pun was intentional. +However, he failed to solve the puzzle. Can you do it?</p> + +<hr style="width: 30%;" /> +<p><a name="X_166_THE_LANDOWNERS_FENCES" id="X_166_THE_LANDOWNERS_FENCES"></a><a href="#X_166_THE_LANDOWNERS_FENCESa"><b>166.—THE LANDOWNER'S FENCES.</b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q166.png" width="600" height="502" alt="" title="" /> +</div> + +<p>The landowner in the illustration is consulting with his bailiff over +a rather puzzling little question. He has a large plan of one of his +fields, in which there are eleven trees. Now, he wants to divide the +field into just eleven enclosures by means of straight fences, so that +every enclosure shall contain one tree as a shelter for his cattle. +How is he to do it with as few fences as possible? Take your pencil +and draw straight lines across the field until you have marked off the +eleven enclosures (and no more), and then see how many fences you +require. Of course the fences may cross one another.</p> + +<hr style="width: 30%;" /> +<p><a name="X_167_THE_WIZARDS_CATS" id="X_167_THE_WIZARDS_CATS"></a><a href="#X_167_THE_WIZARDS_CATSa"><b>167.—THE WIZARD'S CATS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q167.png" width="400" height="392" alt="" title="" /> +</div> + +<p>A wizard placed ten cats inside a magic circle as shown in our +illustration, and hypnotized them so that they should remain +stationary during his pleasure. He then proposed to draw three circles +inside the large one, so that no cat could approach another cat +without crossing a <span class='pagenum'>Pg 43<a name="Page_43" id="Page_43"></a></span>magic circle. Try to draw the three circles so +that every cat has its own enclosure and cannot reach another cat +without crossing a line.</p> + +<hr style="width: 30%;" /> +<p><a name="X_168_THE_CHRISTMAS_PUDDING" id="X_168_THE_CHRISTMAS_PUDDING"></a><a href="#X_168_THE_CHRISTMAS_PUDDINGa"><b>168.—THE CHRISTMAS PUDDING.</b></a></p> + +<p>"Speaking of Christmas puddings," said the host, as he glanced at the +imposing delicacy at the other end of the table. "I am reminded of the +fact that a friend gave me a new puzzle the other day respecting one. +Here it is," he added, diving into his breast pocket.</p> + +<p>"'Problem: To find the contents,' I suppose," said the Eton boy.</p> + +<p>"No; the proof of that is in the eating. I will read you the +conditions."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q168.png" width="400" height="423" alt="" title="" /> +</div> + +<p>"'Cut the pudding into two parts, each of exactly the same size and +shape, without touching any of the plums. The pudding is to be +regarded as a flat disc, not as a sphere.'"</p> + +<p>"Why should you regard a Christmas pudding as a disc? And why should +any reasonable person ever wish to make such an accurate division?" +asked the cynic.</p> + +<p>"It is just a puzzle—a problem in dissection." All in turn had a look +at the puzzle, but nobody succeeded in solving it. It is a little +difficult unless you are acquainted with the principle involved in the +making of such puddings, but easy enough when you know how it is done.</p> + +<hr style="width: 30%;" /> +<p><a name="X_169_A_TANGRAM_PARADOX" id="X_169_A_TANGRAM_PARADOX"></a><a href="#X_169_A_TANGRAM_PARADOXa"><b>169.—A TANGRAM PARADOX.</b></a></p> + +<p>Many pastimes of great antiquity, such as chess, have so developed and +changed down the centuries that their original inventors would +scarcely recognize them. This is not the case with Tangrams, a +recreation that appears to be at least four thousand years old, that +has apparently never been dormant, and that has not been altered or +"improved upon" since the legendary Chinaman Tan first cut out the +seven pieces shown in Diagram I. If you mark the point B, midway +between A and C, on one side of a square of any size, and D, midway +between C and E, on an adjoining side, the direction of the cuts is +too obvious to need further explanation. Every design in this article +is built up from the seven pieces of blackened cardboard. It will at +once be understood that the possible combinations are infinite.</p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/q169a.png" width="300" height="252" alt="" title="" /> +</div> + +<p>The late Mr. Sam Loyd, of New York, who published a small book of very +ingenious designs, possessed the manuscripts of the late Mr. +Challenor, who made a long and close study of Tangrams. This +gentleman, it is said, records that there were originally seven books +of Tangrams, compiled in China two thousand years before the Christian +era. These books are so rare that, after forty years' residence in the +country, he only succeeded in seeing perfect copies of the first and +seventh volumes with fragments of the second. Portions of one of the +books, printed in gold leaf upon parchment, were found in Peking by an +English soldier and sold for three hundred pounds.</p> + +<p>A few years ago a little book came into my possession, from the +library of the late Lewis Carroll, entitled <i>The Fashionable Chinese +Puzzle</i>. It contains three hundred and twenty-three Tangram designs, +mostly nondescript geometrical figures, to be constructed from the +seven pieces. It was "Published by J. and E. Wallis, 42 Skinner +Street, and J. Wallis, Jun., Marine Library, Sidmouth" (South Devon). +There is no date, but the following note fixes the time of publication +pretty closely: "This ingenious contrivance has for some time past +been the favourite amusement of the ex-Emperor Napoleon, who, being +now in a debilitated state and living very retired, passes many hours +a day in thus exercising his patience and ingenuity." The reader will +find, as did the great exile, that much amusement, not wholly +uninstructive, may be derived from forming the designs of others. He +will find many of the illustrations to this article quite easy to +build up, and some rather difficult. Every picture may thus be +regarded as a puzzle.</p> + +<p>But it is another pastime altogether to create new and original +designs of a pictorial character, and it is surprising what +extraordinary scope the Tangrams afford for producing pictures of real +life—angular and often grotesque, it is true, but full of character. +I give an example of a recumbent figure (2) that is particularly +graceful, and only needs some slight reduction of its angularities to +produce an entirely satisfactory outline.</p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/q169b.png" width="300" height="233" alt="" title="" /> +</div> + +<p>As I have referred to the author of <i>Alice in Wonderland</i>, I give also +my designs of the March <span class='pagenum'>Pg 44<a name="Page_44" id="Page_44"></a></span>Hare (3) and the Hatter (4). I also give an +attempt at Napoleon (5), and a very excellent Red Indian with his +Squaw by Mr. Loyd (6 and 7). A large number of other designs will be +found in an article by me in <i>The Strand Magazine</i> for November, 1908.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q169b2.png" width="400" height="322" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 150px;"> +<img src="images/q169c.png" width="150" height="250" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q169d.png" width="400" height="370" alt="" title="" /> +</div> + +<p>On the appearance of this magazine article, the late Sir James Murray, +the eminent philologist, tried, with that amazing industry that +characterized all his work, to trace the word "tangram" to its source. +At length he wrote as follows:—"One of my sons is a professor in the +Anglo-Chinese college at Tientsin. Through him, his colleagues, and +his students, I was able to make inquiries as to the alleged Tan among +Chinese scholars. Our Chinese professor here (Oxford) also took an +interest in the matter and obtained information from the secretary of +the Chinese Legation in London, who is a very eminent representative +of the Chinese literati."</p> + +<p>"The result has been to show that the man Tan, the god Tan, and the +'Book of Tan' are entirely unknown to Chinese literature, history, or +tradition. By most of the learned men the name, or allegation of the +existence, of these had never been heard of. The puzzle is, of course, +well known. It is called in Chinese <i>ch'i ch'iao t'u</i>; literally, +'seven-ingenious-plan' or 'ingenious-puzzle figure of seven pieces.' +No name approaching 'tangram,' or even 'tan,' occurs in Chinese, and +the only suggestions for the latter were the Chinese <i>t'an</i>, 'to +extend'; or <i>t'ang</i>, Cantonese dialect for 'Chinese.' It was suggested +that probably some American or Englishman who knew a little Chinese or +Cantonese, wanting a name for the puzzle, might concoct one out of one +of these words and the European ending 'gram.' I should say the name +'tangram' was probably invented by an American some little time before +1864 and after 1847, but I cannot find it in print before the 1864 +edition of Webster. I have therefore had to deal very shortly with the +word in the dictionary, telling what it is applied to and what +conjectures or guesses have been made at the name, and giving a few +quotations, one from your own article, which has enabled me to make +more of the subject than I could otherwise have done."</p> + +<p>Several correspondents have informed me that they possess, or had +possessed, specimens of the old Chinese books. An American gentleman +writes to me as follows:—"I have in my possession a book made of +tissue paper, printed in black (with a Chinese inscription on the +front page), containing over three hundred designs, which belongs to +the box of 'tangrams,' which I also own. The blocks are seven in +number, made of mother-of-pearl, highly polished and finely engraved +on either side. These are contained in a rosewood box 2<sup>1</sup>/<sub>8</sub> +in. square. My great uncle, ——, was one of the first missionaries to +visit China. This box and book, along with quite a collection of other +relics, were sent to my grandfather and descended to myself."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q169e.png" width="400" height="314" alt="" title="" /> +</div> + +<p>My correspondent kindly supplied me with rubbings of the Tangrams, +from which it is clear that they are cut in the exact proportions that +I have indicated. I reproduce the Chinese inscription (8) for this +reason. The owner of the book informs me that he has submitted it to a +number of Chinamen in the United States and offered as much as a +dollar for a translation. But they all steadfastly refused to read the +words, offering the lame excuse that the inscription is Japanese. +Natives of Japan, however, insist that it is Chinese. Is there +something occult and esoteric about Tangrams, that <span class='pagenum'>Pg 45<a name="Page_45" id="Page_45"></a></span>it is so difficult +to lift the veil? Perhaps this page will come under the eye of some +reader acquainted with the Chinese language, who will supply the +required translation, which may, or may not, throw a little light on +this curious question.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q169f.png" width="400" height="246" alt="" title="" /> +</div> + +<p>By using several sets of Tangrams at the same time we may construct +more ambitious pictures. I was advised by a friend not to send my +picture, "A Game of Billiards" (9), to the Academy. He assured me that +it would not be accepted because the "judges are so hide-bound by +convention." Perhaps he was right, and it will be more appreciated by +Post-impressionists and Cubists. The players are considering a very +delicate stroke at the top of the table. Of course, the two men, the +table, and the clock are formed from four sets of Tangrams. My second +picture is named "The Orchestra" (10), and it was designed for the +decoration of a large hall of music. Here we have the conductor, the +pianist, the fat little cornet-player, the left-handed player of the +double-bass, whose attitude is life-like, though he does stand at an +unusual distance from his instrument, and the drummer-boy, with his +imposing music-stand. The dog at the back of the pianoforte is not +howling: he is an appreciative listener.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q169g.png" width="600" height="233" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q169h.png" width="400" height="292" alt="" title="" /> +</div> + +<p>One remarkable thing about these Tangram pictures is that they suggest +to the imagination such a lot that is not really there. Who, for +example, can look for a few minutes at Lady Belinda (11) and the Dutch +girl (12) without soon feeling the haughty expression in the one case +and the arch look in the other? Then look again at the stork (13), and +see how it is suggested to the mind that the leg is actually much more +slender than any one of the pieces employed. It is really an optical +illusion. Again, notice in the case of the yacht (14) how, by leaving +that little angular point at the top, a complete mast is suggested. If +you place your Tangrams together on white paper so that they do not +quite touch one another, in some cases the effect is improved by the +white lines; in other cases it is almost destroyed.</p> + +<div class="figcenter" style="width: 499px;"> +<img src="images/q169i.png" width="499" height="292" alt="" title="" /> +</div> + +<p>Finally, I give an example from the many curious paradoxes that one +happens upon in manipulating Tangrams. I show designs of <span class='pagenum'>Pg 46<a name="Page_46" id="Page_46"></a></span>two +dignified individuals (15 and 16) who appear to be exactly alike, +except for the fact that one has a foot and the other has not. Now, +both of these figures are made from the same seven Tangrams. Where +does the second man get his foot from?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q169j.png" width="400" height="361" alt="" title="" /> +</div> + +<hr style="width: 65%;" /> +<h2><a name="PATCHWORK_PUZZLES" id="PATCHWORK_PUZZLES"></a><a href="#CONTENTS">PATCHWORK PUZZLES.</a></h2> + +<p class='center'>"Of shreds and patches."—<i>Hamlet</i>, iii. 4.</p> + +<hr style="width: 30%;" /> +<p><a name="X_170_THE_CUSHION_COVERS" id="X_170_THE_CUSHION_COVERS"></a><a href="#X_170_THE_CUSHION_COVERSa"><b>170.—THE CUSHION COVERS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q170.png" width="400" height="398" alt="" title="" /> +</div> + +<p>The above represents a square of brocade. A lady wishes to cut it in +four pieces so that two pieces will form one perfectly square cushion +top, and the remaining two pieces another square cushion top. How is +she to do it? Of course, she can only cut along the lines that divide +the twenty-five squares, and the pattern must "match" properly without +any irregularity whatever in the design of the material. There is only +one way of doing it. Can you find it?</p> + +<hr style="width: 30%;" /> +<p><a name="X_171_THE_BANNER_PUZZLE" id="X_171_THE_BANNER_PUZZLE"></a><a href="#X_171_THE_BANNER_PUZZLEa"><b>171.—THE BANNER PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q171.png" width="400" height="400" alt="" title="" /> +</div> + +<p>A Lady had a square piece of bunting with two lions on it, of which +the illustration is an exactly reproduced reduction. She wished to cut +the stuff into pieces that would fit together and form two square +banners with a lion on each banner. She discovered that this could be +done in as few as four pieces. How did she manage it? Of course, to +cut the British Lion would be an unpardonable offence, so you must be +careful that no cut passes through any portion of either of them. +Ladies are informed that no allowance whatever has to be made for +"turnings," and no part of the material may be wasted. It is quite a +simple little dissection puzzle if rightly attacked. Remember that the +banners have to be perfect squares, though they need not be both of +the same size.</p> + +<hr style="width: 30%;" /> +<p><a name="X_172_MRS_SMILEYS_CHRISTMAS_PRESENT" id="X_172_MRS_SMILEYS_CHRISTMAS_PRESENT"></a><a href="#X_172_MRS_SMILEYS_CHRISTMAS_PRESENTa"><b>172.—MRS. SMILEY'S CHRISTMAS PRESENT.</b></a></p> + +<p>Mrs. Smiley's expression of pleasure was sincere when her six +granddaughters sent to her, as a Christmas present, a very pretty +patchwork quilt, which they had made with their own hands. It was +constructed of square pieces of silk material, all of one size, and as +they made a large quilt with fourteen of these little squares on each +side, it is obvious that just 196 pieces had been stitched into it. +Now, the six granddaughters each contributed a part of the work in the +form of a perfect square (all six portions being different in size), +but in order to join them up to form the square quilt it was necessary +that the work of one girl should be unpicked into three separate +pieces. Can you show how the joins might have been made? Of course, no +portion can be turned over.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q172.png" width="600" height="465" alt="" title="" /> +</div> + +<p><span class='pagenum'>Pg 47<a name="Page_47" id="Page_47"></a></span></p> + +<hr style="width: 30%;" /> +<p><a name="X_173_MRS_PERKINSS_QUILT" id="X_173_MRS_PERKINSS_QUILT"></a><a href="#X_173_MRS_PERKINSS_QUILTa"><b>173.—MRS. PERKINS'S QUILT.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q173.png" width="400" height="461" alt="" title="" /> +</div> + +<p>It will be seen that in this case the square patchwork quilt is built +up of 169 pieces. The puzzle is to find the smallest possible number +of square portions of which the quilt could be composed and show how +they might be joined together. Or, to put it the reverse way, divide +the quilt into as few square portions as possible by merely cutting +the stitches.</p> + +<hr style="width: 30%;" /> +<p><a name="X_174_THE_SQUARES_OF_BROCADE" id="X_174_THE_SQUARES_OF_BROCADE"></a><a href="#X_174_THE_SQUARES_OF_BROCADEa"><b>174.—THE SQUARES OF BROCADE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q174a.png" width="400" height="399" alt="" title="" /> +</div> + +<p>I happened to be paying a call at the house of a lady, when I took up +from a table two lovely squares of brocade. They were beautiful +specimens of Eastern workmanship—both of the same design, a delicate +chequered pattern.</p> + +<p>"Are they not exquisite?" said my friend. "They were brought to me by +a cousin who has just returned from India. Now, I want you <span class='pagenum'>Pg 48<a name="Page_48" id="Page_48"></a></span>to give me +a little assistance. You see, I have decided to join them together so +as to make one large square cushion-cover. How should I do this so as +to mutilate the material as little as possible? Of course I propose to +make my cuts only along the lines that divide the little chequers."</p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/q174b.png" width="300" height="300" alt="" title="" /> +</div> + +<p>I cut the two squares in the manner desired into four pieces that +would fit together and form another larger square, taking care that +the pattern should match properly, and when I had finished I noticed +that two of the pieces were of exactly the same area; that is, each of +the two contained the same number of chequers. Can you show how the +cuts were made in accordance with these conditions?</p> + +<hr style="width: 30%;" /> +<p><a name="X_175_ANOTHER_PATCHWORK_PUZZLE" id="X_175_ANOTHER_PATCHWORK_PUZZLE"></a><a href="#X_175_ANOTHER_PATCHWORK_PUZZLEa"><b>175.—ANOTHER PATCHWORK PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 550px;"> +<img src="images/q175.png" width="550" height="383" alt="" title="" /> +</div> + +<p>A lady was presented, by two of her girl friends, with the pretty +pieces of silk patchwork shown in our illustration. It will be seen +that both pieces are made up of squares all of the same size—one +12x12 and the other 5x5. She proposes to join them together and make +one square patchwork quilt, 13x13, but, of course, she will not cut +any of the material—merely cut the stitches where necessary and join +together again. What perplexes her is this. A friend assures her that +there need be no more than four pieces in all to join up for the new +quilt. Could you show her how this little needlework puzzle is to be +solved in so few pieces?</p> + +<hr style="width: 30%;" /> +<p><a name="X_176_LINOLEUM_CUTTING" id="X_176_LINOLEUM_CUTTING"></a><a href="#X_176_LINOLEUM_CUTTINGa"><b>176.—LINOLEUM CUTTING.</b></a></p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/q176.png" width="500" height="288" alt="" title="" /> +</div> + +<p>The diagram herewith represents two separate pieces of linoleum. The +chequered pattern is not repeated at the back, so that the pieces +cannot be turned over. The puzzle is to cut the two squares into four +pieces so that they shall fit together and form one perfect square +10×10, so that the pattern shall properly <span class='pagenum'>Pg 49<a name="Page_49" id="Page_49"></a></span>match, and so that the +larger piece shall have as small a portion as possible cut from it.</p> + +<hr style="width: 30%;" /> +<p><a name="X_177_ANOTHER_LINOLEUM_PUZZLE" id="X_177_ANOTHER_LINOLEUM_PUZZLE"></a><a href="#X_177_ANOTHER_LINOLEUM_PUZZLEa"><b>177.—ANOTHER LINOLEUM PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q177.png" width="400" height="200" alt="" title="" /> +</div> + +<p>Can you cut this piece of linoleum into four pieces that will fit +together and form a perfect square? Of course the cuts may only be +made along the lines.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="VARIOUS_GEOMETRICAL_PUZZLES" id="VARIOUS_GEOMETRICAL_PUZZLES"></a><a href="#CONTENTS">VARIOUS GEOMETRICAL PUZZLES.</a></h2> + +<p class='center'> +"So various are the tastes of men."<br /> +<span style="margin-left: 8em;">MARK AKENSIDE.<br /></span> +</p> + +<hr style="width: 30%;" /> +<p><a name="X_178_THE_CARDBOARD_BOX" id="X_178_THE_CARDBOARD_BOX"></a><a href="#X_178_THE_CARDBOARD_BOXa"><b>178.—THE CARDBOARD BOX.</b></a></p> + +<p>This puzzle is not difficult, but it will be found entertaining to +discover the simple rule for its solution. I have a rectangular +cardboard box. The top has an area of 120 square inches, the side 96 +square inches, and the end 80 square inches. What are the exact +dimensions of the box?</p> + +<hr style="width: 30%;" /> +<p><a name="X_179_STEALING_THE_BELL-ROPES" id="X_179_STEALING_THE_BELL-ROPES"></a><a href="#X_179_STEALING_THE_BELL-ROPESa"><b>179.—STEALING THE BELL-ROPES.</b></a></p> + +<p>Two men broke into a church tower one night to steal the bell-ropes. +The two ropes passed through holes in the wooden ceiling high above +them, and they lost no time in climbing to the top. Then one man drew +his knife and cut the rope above his head, in consequence of which he +fell to the floor and was badly injured. His fellow-thief called out +that it served him right for being such a fool. He said that he should +have done as he was doing, upon which he cut the rope below the place +at which he held on. Then, to his dismay, he found that he was in no +better plight, for, after hanging on as long as his strength lasted, +he was compelled to let go and fall beside his comrade. Here they were +both found the next morning with their limbs broken. How far did they +fall? One of the ropes when they found it was just touching the floor, +and when you pulled the end to the wall, keeping the rope taut, it +touched a point just three inches above the floor, and the wall was +four feet from the rope when it hung at rest. How long was the rope +from floor to ceiling?</p> + +<hr style="width: 30%;" /> +<p><a name="X_180_THE_FOUR_SONS" id="X_180_THE_FOUR_SONS"></a><a href="#X_180_THE_FOUR_SONSa"><b>180.—THE FOUR SONS.</b></a></p> + +<p>Readers will recognize the diagram as a familiar friend of their +youth. A man possessed a square-shaped estate. He bequeathed to his +widow the quarter of it that is shaded off. The remainder was to be +divided equitably amongst his four sons, so that each should receive +land of exactly the same area and exactly similar in shape. We are +shown how this was done. But the remainder of the story is not so +generally known. In the centre of the estate was a well, indicated by +the dark spot, and Benjamin, Charles, and David complained that the +division was not "equitable," since Alfred had access to this well, +while they could not reach it without trespassing on somebody else's +land. The puzzle is to show how the estate is to be apportioned so +that each son shall have land of the same shape and area, and each +have access to the well without going off his own land.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q180.png" width="400" height="392" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_181_THE_THREE_RAILWAY_STATIONS" id="X_181_THE_THREE_RAILWAY_STATIONS"></a><a href="#X_181_THE_THREE_RAILWAY_STATIONSa"><b>181.—THE THREE RAILWAY STATIONS.</b></a></p> + +<p>As I sat in a railway carriage I noticed at the other end of the +compartment a worthy squire, whom I knew by sight, engaged in +conversation with another passenger, who was evidently a friend of +his.</p> + +<p>"How far have you to drive to your place from the railway station?" +asked the stranger.</p> + +<p>"Well," replied the squire, "if I get out at Appleford, it is just the +same distance as if I go to Bridgefield, another fifteen miles farther +on; and if I changed at Appleford and went thirteen miles from there +to Carterton, it would still be the same distance. You see, I am +equidistant from the three stations, so I get a good choice of +trains."</p> + +<p>Now I happened to know that Bridgefield is just fourteen miles from +Carterton, so I amused myself in working out the exact distance that +the squire had to drive home whichever station he got out at. What was +the distance?</p> + +<hr style="width: 30%;" /> +<p><a name="X_182_THE_GARDEN_PUZZLE" id="X_182_THE_GARDEN_PUZZLE"></a><a href="#X_182_THE_GARDEN_PUZZLEa"><b>182.—THE GARDEN PUZZLE.</b></a></p> + +<p>Professor Rackbrain tells me that he was recently smoking a friendly +pipe under a tree in the garden of a country acquaintance. The garden +was enclosed by four straight walls, and his friend informed him that +he had measured these and found the lengths to be 80, 45, 100, and 63 +yards respectively. "Then," said the professor, "we can calculate the +exact area of the garden." "Impossible," his host replied, <span class='pagenum'>Pg 50<a name="Page_50" id="Page_50"></a></span>"because +you can get an infinite number of different shapes with those four +sides." "But you forget," Rackbrane said, with a twinkle in his eye, +"that you told me once you had planted this tree equidistant from all +the four corners of the garden." Can you work out the garden's area?</p> + +<hr style="width: 30%;" /> +<p><a name="X_183_DRAWING_A_SPIRAL" id="X_183_DRAWING_A_SPIRAL"></a><a href="#X_183_DRAWING_A_SPIRALa"><b>183.—DRAWING A SPIRAL.</b></a></p> + +<p>If you hold the page horizontally and give it a quick rotary motion +while looking at the centre of the spiral, it will appear to revolve. +Perhaps a good many readers are acquainted with this little optical +illusion. But the puzzle is to show how I was able to draw this spiral +with so much exactitude without using anything but a pair of compasses +and the sheet of paper on which the diagram was made. How would you +proceed in such circumstances?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q183.png" width="400" height="392" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_184_HOW_TO_DRAW_AN_OVAL" id="X_184_HOW_TO_DRAW_AN_OVAL"></a><a href="#X_184_HOW_TO_DRAW_AN_OVALa"><b>184.—HOW TO DRAW AN OVAL.</b></a></p> + +<p>Can you draw a perfect oval on a sheet of paper with one sweep of the +compasses? It is one of the easiest things in the world when you know +how.</p> + +<hr style="width: 30%;" /> +<p><a name="X_185_ST_GEORGES_BANNER" id="X_185_ST_GEORGES_BANNER"></a><a href="#X_185_ST_GEORGES_BANNERa"><b>185.—ST. GEORGE'S BANNER.</b></a></p> + +<p>At a celebration of the national festival of St. George's Day I was +contemplating the familiar banner of the patron saint of our country. +We all know the red cross on a white ground, shown in our +illustration. This is the banner of St. George. The banner of St. +Andrew (Scotland) is a white "St. Andrew's Cross" on a blue ground. +That of St. Patrick (Ireland) is a similar cross in red on a white +ground. These three are united in one to form our Union Jack.</p> + +<p>Now on looking at St. George's banner it occurred to me that the +following question would make a simple but pretty little puzzle. +Supposing the flag measures four feet by three feet, how wide must the +arm of the cross be if it is required that there shall be used just +the same quantity of red and of white bunting?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q185.png" width="400" height="420" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_186_THE_CLOTHES_LINE_PUZZLE" id="X_186_THE_CLOTHES_LINE_PUZZLE"></a><a href="#X_186_THE_CLOTHES_LINE_PUZZLEa"><b>186.—THE CLOTHES LINE PUZZLE.</b></a></p> + +<p>A boy tied a clothes line from the top of each of two poles to the +base of the other. He then proposed to his father the following +question. As one pole was exactly seven feet above the ground and the +other exactly five feet, what was the height from the ground where the +two cords crossed one another?</p> + +<hr style="width: 30%;" /> +<p><a name="X_187_THE_MILKMAID_PUZZLE" id="X_187_THE_MILKMAID_PUZZLE"></a><a href="#X_187_THE_MILKMAID_PUZZLEa"><b>187.—THE MILKMAID PUZZLE.</b></a></p> + +<p>Here is a little pastoral puzzle that the reader may, at first sight, +be led into supposing is very profound, involving deep calculations. +He may even say that it is quite impossible to give any answer unless +we are told something definite as to the distances. And yet it is +really quite "childlike and bland."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q187.png" width="400" height="349" alt="" title="" /> +</div> + +<p><span class='pagenum'>Pg 51<a name="Page_51" id="Page_51"></a></span>In the corner of a field is seen a milkmaid milking a cow, and on the +other side of the field is the dairy where the extract has to be +deposited. But it has been noticed that the young woman always goes +down to the river with her pail before returning to the dairy. Here +the suspicious reader will perhaps ask why she pays these visits to +the river. I can only reply that it is no business of ours. The +alleged milk is entirely for local consumption.</p> + +<p> +<span style="margin-left: 2em;">"Where are you going to, my pretty maid?"</span><br /> +<span style="margin-left: 2em;">"Down to the river, sir," she said.</span><br /> +<span style="margin-left: 2em;">"I'll <i>not</i> choose your dairy, my pretty maid."</span><br /> +<span style="margin-left: 2em;">"Nobody axed you, sir," she said.</span><br /> +</p> + +<p>If one had any curiosity in the matter, such an independent spirit +would entirely disarm one. So we will pass from the point of +commercial morality to the subject of the puzzle.</p> + +<p>Draw a line from the milking-stool down to the river and thence to the +door of the dairy, which shall indicate the shortest possible route +for the milkmaid. That is all. It is quite easy to indicate the exact +spot on the bank of the river to which she should direct her steps if +she wants as short a walk as possible. Can you find that spot?</p> + +<hr style="width: 30%;" /> +<p><a name="X_188_THE_BALL_PROBLEM" id="X_188_THE_BALL_PROBLEM"></a><a href="#X_188_THE_BALL_PROBLEMa"><b>188.—THE BALL PROBLEM.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q188.png" width="400" height="312" alt="" title="" /> +</div> + +<p>A stonemason was engaged the other day in cutting out a round ball for +the purpose of some architectural decoration, when a smart schoolboy +came upon the scene.</p> + +<p>"Look here," said the mason, "you seem to be a sharp youngster, can +you tell me this? If I placed this ball on the level ground, how many +other balls of the same size could I lay around it (also on the +ground) so that every ball should touch this one?"</p> + +<p>The boy at once gave the correct answer, and then put this little +question to the mason:—</p> + +<p>"If the surface of that ball contained just as many square feet as its +volume contained cubic feet, what would be the length of its +diameter?"</p> + +<p>The stonemason could not give an answer. Could you have replied +correctly to the mason's and the boy's questions?</p> + +<hr style="width: 30%;" /> +<p><a name="X_189_THE_YORKSHIRE_ESTATES" id="X_189_THE_YORKSHIRE_ESTATES"></a><a href="#X_189_THE_YORKSHIRE_ESTATESa"><b>189.—THE YORKSHIRE ESTATES.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q189.png" width="400" height="278" alt="" title="" /> +</div> + +<p>I was on a visit to one of the large towns of Yorkshire. While walking +to the railway station on the day of my departure a man thrust a +hand-bill upon me, and I took this into the railway carriage and read +it at my leisure. It informed me that three Yorkshire neighbouring +estates were to be offered for sale. Each estate was square in shape, +and they joined one another at their corners, just as shown in the +diagram. Estate A contains exactly 370 acres, B contains 116 acres, +and C 74 acres.</p> + +<p>Now, the little triangular bit of land enclosed by the three square +estates was not offered for sale, and, for no reason in particular, I +became curious as to the area of that piece. How many acres did it +contain?</p> + +<hr style="width: 30%;" /> +<p><a name="X_190_FARMER_WURZELS_ESTATE" id="X_190_FARMER_WURZELS_ESTATE"></a><a href="#X_190_FARMER_WURZELS_ESTATEa"><b>190.—FARMER WURZEL'S ESTATE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q190.png" width="400" height="376" alt="" title="" /> +</div> + +<p>I will now present another land problem. The demonstration of the +answer that I shall give will, I think, be found both interesting and +easy of comprehension.</p> + +<p>Farmer Wurzel owned the three square fields shown in the annexed plan, +containing respectively 18, 20, and 26 acres. In order to get a +ring-fence round his property he bought the <span class='pagenum'>Pg 52<a name="Page_52" id="Page_52"></a></span>four intervening +triangular fields. The puzzle is to discover what was then the whole +area of his estate.</p> + +<hr style="width: 30%;" /> +<p><a name="X_191_THE_CRESCENT_PUZZLE" id="X_191_THE_CRESCENT_PUZZLE"></a><a href="#X_191_THE_CRESCENT_PUZZLEa"><b>191.—THE CRESCENT PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q191.png" width="400" height="381" alt="" title="" /> +</div> + +<p>Here is an easy geometrical puzzle. The crescent is formed by two +circles, and C is the centre of the larger circle. The width of the +crescent between B and D is 9 inches, and between E and F 5 inches. +What are the diameters of the two circles?</p> + +<hr style="width: 30%;" /> +<p><a name="X_192_THE_PUZZLE_WALL" id="X_192_THE_PUZZLE_WALL"></a><a href="#X_192_THE_PUZZLE_WALLa"><b>192.—THE PUZZLE WALL.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q192.png" width="400" height="396" alt="" title="" /> +</div> + +<p>There was a small lake, around which four poor men built their +cottages. Four rich men afterwards built their mansions, as shown in +the illustration, and they wished to have the lake to themselves, so +they instructed a builder to put up the shortest possible wall that +would exclude the cottagers, but give themselves free access to the +lake. How was the wall to be built?</p> + +<hr style="width: 30%;" /> +<p><a name="X_193_THE_SHEEP_FOLD" id="X_193_THE_SHEEP_FOLD"></a><a href="#X_193_THE_SHEEP_FOLDa"><b>193.—THE SHEEP-FOLD.</b></a></p> + +<p>It is a curious fact that the answers always given to some of the +best-known puzzles that appear in every little book of fireside +recreations that has been published for the last fifty or a hundred +years are either quite unsatisfactory or clearly wrong. Yet nobody +ever seems to detect their faults. Here is an example:—A farmer had a +pen made of fifty hurdles, capable of holding a hundred sheep only. +Supposing he wanted to make it sufficiently large to hold double that +number, how many additional hurdles must he have?</p> + +<hr style="width: 30%;" /> +<p><a name="X_194_THE_GARDEN_WALLS" id="X_194_THE_GARDEN_WALLS"></a><a href="#X_194_THE_GARDEN_WALLSa"><b>194.—THE GARDEN WALLS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q194.png" width="400" height="409" alt="" title="" /> +</div> + +<p>A speculative country builder has a circular field, on which he has +erected four cottages, as shown in the illustration. The field is +surrounded by a brick wall, and the owner undertook to put up three +other brick walls, so that the neighbours should not be overlooked by +each other, but the four tenants insist that there shall be no +favouritism, and that each shall have exactly the same length of wall +space for his wall fruit trees. The puzzle is to show how the three +walls may be built so that each tenant shall have the same area of +ground, and precisely the same length of wall.</p> + +<p>Of course, each garden must be entirely enclosed by its walls, and it +must be possible to prove that each garden has exactly the same length +of wall. If the puzzle is properly solved no figures are necessary.</p> + +<hr style="width: 30%;" /> +<p><a name="X_195_LADY_BELINDAS_GARDEN" id="X_195_LADY_BELINDAS_GARDEN"></a><a href="#X_195_LADY_BELINDAS_GARDENa"><b>195.—LADY BELINDA'S GARDEN.</b></a></p> + +<p>Lady Belinda is an enthusiastic gardener. In the illustration she is +depicted in the act of worrying out a pleasant little problem which I +will relate. One of her gardens is oblong in shape, enclosed by a high +holly hedge, and she is turning it into a rosary for the cultivation +of <span class='pagenum'>Pg 53<a name="Page_53" id="Page_53"></a></span>some of her choicest roses. She wants to devote exactly half of +the area of the garden to the flowers, in one large bed, and the other +half to be a path going all round it of equal breadth throughout. Such +a garden is shown in the diagram at the foot of the picture. How is +she to mark out the garden under these simple conditions? She has only +a tape, the length of the garden, to do it with, and, as the holly +hedge is so thick and dense, she must make all her measurements +inside. Lady Belinda did not know the exact dimensions of the garden, +and, as it was not necessary for her to know, I also give no +dimensions. It is quite a simple task no matter what the size or +proportions of the garden may be. Yet how many lady gardeners would +know just how to proceed? The tape may be quite plain—that is, it +need not be a graduated measure.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q195.png" width="400" height="351" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_196_THE_TETHERED_GOAT" id="X_196_THE_TETHERED_GOAT"></a><a href="#X_196_THE_TETHERED_GOATa"><b>196.—THE TETHERED GOAT.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q196.png" width="400" height="356" alt="" title="" /> +</div> + +<p>Here is a little problem that everybody should know how to solve. The +goat is placed in a half-acre meadow, that is in shape an equilateral +triangle. It is tethered to a post at one corner of the field. What +should be the length of the tether (to the nearest inch) in order that +the goat shall be able to eat just half the grass in the field? It is +assumed that the goat can feed to the end of the tether.</p> + +<hr style="width: 30%;" /> +<p><a name="X_197_THE_COMPASSES_PUZZLE" id="X_197_THE_COMPASSES_PUZZLE"></a><a href="#X_197_THE_COMPASSES_PUZZLEa"><b>197.—THE COMPASSES PUZZLE.</b></a></p> + +<p>It is curious how an added condition or restriction will sometimes +convert an absurdly easy puzzle into an interesting and perhaps +difficult one. I remember buying in the street many years ago a little +mechanical puzzle that had a tremendous sale at the time. It consisted +of a medal with holes in it, and the puzzle was to work a ring with a +gap in it from hole to hole until it was finally detached. As I was +walking along the street I very soon acquired the trick of taking off +the ring with one hand while holding the puzzle in my pocket. A friend +to whom I showed the little feat set about accomplishing it himself, +and when I met him some days afterwards he exhibited his proficiency +in the art. But he was a little taken aback when I then took the +puzzle from him and, while simply holding the medal between the finger +and thumb of one hand, by a series of little shakes and jerks caused +the ring, without my even touching it, to fall off upon the floor. The +following little poser will probably prove a rather tough nut for a +great many readers, simply on account of the restricted conditions:—</p> + +<p>Show how to find exactly the middle of any straight line by means of +the compasses only. You are not allowed to use any ruler, pencil, or +other article—only the compasses; and no trick or dodge, such as +folding the paper, will be permitted. You must simply use the +compasses in the ordinary legitimate way.</p> + +<hr style="width: 30%;" /> +<p><a name="X_198_THE_EIGHT_STICKS" id="X_198_THE_EIGHT_STICKS"></a><a href="#X_198_THE_EIGHT_STICKSa"><b>198.—THE EIGHT STICKS.</b></a></p> + +<p>I have eight sticks, four of them being exactly half the length of the +others. I lay every one of these on the table, so that they enclose +three squares, all of the same size. How do I do it? There must be no +loose ends hanging over.</p> + +<hr style="width: 30%;" /> +<p><a name="X_199_PAPAS_PUZZLE" id="X_199_PAPAS_PUZZLE"></a><a href="#X_199_PAPAS_PUZZLEa"><b>199.—PAPA'S PUZZLE.</b></a></p> + +<p>Here is a puzzle by Pappus, who lived at Alexandria about the end of +the third century. It is the fifth proposition in the eighth book of +his <i>Mathematical Collections</i>. I give it in the form that I presented +it some years ago under the title "Papa's Puzzle," just to see how +many readers would discover that it was by Pappus himself. "The little +maid's papa has taken two different-sized rectangular pieces of +cardboard, and has clipped off a triangular piece from one of them, so +that when it is suspended by a thread from the point A it hangs with +the long side perfectly horizontal, as shown in the illustration. He +has perplexed the child by asking her to find the point A on the other +card, so as to produce a similar result when cut and suspended by a +thread." Of course, the point must not be <span class='pagenum'>Pg 54<a name="Page_54" id="Page_54"></a></span>found by trial clippings. A +curious and pretty point is involved in this setting of the puzzle. +Can the reader discover it?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q199.png" width="400" height="411" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_200_A_KITE-FLYING_PUZZLE" id="X_200_A_KITE-FLYING_PUZZLE"></a><a href="#X_200_A_KITE-FLYING_PUZZLEa"><b>200.—A KITE-FLYING PUZZLE.</b></a></p> + +<p>While accompanying my friend Professor Highflite during a scientific +kite-flying competition on the South Downs of Sussex I was led into a +little calculation that ought to interest my readers. The Professor +was paying out the wire to which his kite was attached from a winch on +which it had been rolled into a perfectly spherical form. This ball of +wire was just two feet in diameter, and the wire had a diameter of +one-hundredth of an inch. What was the length of the wire?</p> + +<p>Now, a simple little question like this that everybody can perfectly +understand will puzzle many people to answer in any way. Let us see +whether, without going into any profound mathematical calculations, we +can get the answer roughly—say, within a mile of what is correct! We +will assume that when the wire is all wound up the ball is perfectly +solid throughout, and that no allowance has to be made for the axle +that passes through it. With that simplification, I wonder how many +readers can state within even a mile of the correct answer the length +of that wire.</p> + +<hr style="width: 30%;" /> +<p><a name="X_201_HOW_TO_MAKE_CISTERNS" id="X_201_HOW_TO_MAKE_CISTERNS"></a><a href="#X_201_HOW_TO_MAKE_CISTERNSa"><b>201.—HOW TO MAKE CISTERNS.</b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q201.png" width="600" height="472" alt="" title="" /> +</div> + +<p>Our friend in the illustration has a large sheet of zinc, measuring +(before cutting) eight feet by three feet, and he has cut out square +pieces (all of the same size) from the four corners and now proposes +to fold up the sides, solder the edges, and make a cistern. But the +point that puzzles him is this: Has he cut out those square pieces of +the correct size in order that the cistern may hold the greatest +possible quantity of water? You see, if you cut them very small you +get a <span class='pagenum'>Pg 55<a name="Page_55" id="Page_55"></a></span>very shallow cistern; if you cut them large you get a tall and +slender one. It is all a question of finding a way of cutting put +these four square pieces exactly the right size. How are we to avoid +making them too small or too large?</p> + +<hr style="width: 30%;" /> +<p><a name="X_202_THE_CONE_PUZZLE" id="X_202_THE_CONE_PUZZLE"></a><a href="#X_202_THE_CONE_PUZZLEa"><b>202.—THE CONE PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q202.png" width="400" height="194" alt="" title="" /> +</div> + +<p>I have a wooden cone, as shown in Fig. 1. How am I to cut out of it +the greatest possible cylinder? It will be seen that I can cut out one +that is long and slender, like Fig. 2, or short and thick, like Fig. +3. But neither is the largest possible. A child could tell you where +to cut, if he knew the rule. Can you find this simple rule?</p> + +<hr style="width: 30%;" /> +<p><a name="X_203_CONCERNING_WHEELS" id="X_203_CONCERNING_WHEELS"></a><a href="#X_203_CONCERNING_WHEELSa"><b>203.—CONCERNING WHEELS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q203.png" width="400" height="537" alt="" title="" /> +</div> + +<p>There are some curious facts concerning the movements of wheels that +are apt to perplex the novice. For example: when a railway train is +travelling from London to Crewe certain parts of the train at any +given moment are actually moving from Crewe towards London. Can you +indicate those parts? It seems absurd that parts of the same train +can at any time travel in opposite directions, but such is the case.</p> + +<p>In the accompanying illustration we have two wheels. The lower one is +supposed to be fixed and the upper one running round it in the +direction of the arrows. Now, how many times does the upper wheel turn +on its own axis in making a complete revolution of the other wheel? Do +not be in a hurry with your answer, or you are almost certain to be +wrong. Experiment with two pennies on the table and the correct answer +will surprise you, when you succeed in seeing it.</p> + +<hr style="width: 30%;" /> +<p><a name="X_204_A_NEW_MATCH_PUZZLE" id="X_204_A_NEW_MATCH_PUZZLE"></a><a href="#X_204_A_NEW_MATCH_PUZZLEa"><b>204.—A NEW MATCH PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q204.png" width="400" height="329" alt="" title="" /> +</div> + +<p>In the illustration eighteen matches are shown arranged so that they +enclose two spaces, one just twice as large as the other. Can you +rearrange them (1) so as to enclose two four-sided spaces, one exactly +three times as large as the other, and (2) so as to enclose two +five-sided spaces, one exactly three times as large as the other? All +the eighteen matches must be fairly used in each case; the two spaces +must be quite detached, and there must be no loose ends or duplicated +matches.</p> + +<hr style="width: 30%;" /> +<p><a name="X_205_THE_SIX_SHEEP-PENS" id="X_205_THE_SIX_SHEEP-PENS"></a><a href="#X_205_THE_SIX_SHEEP-PENSa"><b>205.—THE SIX SHEEP-PENS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q205.png" width="400" height="154" alt="" title="" /> +</div> + +<p>Here is a new little puzzle with matches. It will be seen in the +illustration that thirteen matches, representing a farmer's hurdles, +have been so placed that they enclose six sheep-pens all of the same +size. Now, one of these hurdles was stolen, and the farmer wanted +still to enclose six pens of equal size with the remaining twelve. How +was he to do it? All the twelve matches must be fairly used, and there +must be no duplicated matches or loose ends.</p> + + + +<hr style="width: 65%;" /><p><span class='pagenum'>Pg 56<a name="Page_56" id="Page_56"></a></span></p> +<h2><a name="POINTS_AND_LINES_PROBLEMS" id="POINTS_AND_LINES_PROBLEMS"></a><a href="#CONTENTS">POINTS AND LINES PROBLEMS.</a></h2> + + +<p class='center'>"Line upon line, line upon line; here a little and there a +little."—<i>Isa</i>. xxviii. 10.</p> + +<p>What are known as "Points and Lines" puzzles are found very +interesting by many people. The most familiar example, here given, to +plant nine trees so that they shall form ten straight rows with three +trees in every row, is attributed to Sir Isaac Newton, but the +earliest collection of such puzzles is, I believe, in a rare little +book that I possess—published in 1821—<i>Rational Amusement for Winter +Evenings</i>, by John Jackson. The author gives ten examples of "Trees +planted in Rows."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/points.png" width="400" height="208" alt="" title="" /> +</div> + +<p>These tree-planting puzzles have always been a matter of great +perplexity. They are real "puzzles," in the truest sense of the word, +because nobody has yet succeeded in finding a direct and certain way +of solving them. They demand the exercise of sagacity, ingenuity, and +patience, and what we call "luck" is also sometimes of service. +Perhaps some day a genius will discover the key to the whole mystery. +Remember that the trees must be regarded as mere points, for if we +were allowed to make our trees big enough we might easily "fudge" our +diagrams and get in a few extra straight rows that were more apparent +than real.</p> + +<hr style="width: 30%;" /> +<p><a name="X_206_THE_KING_AND_THE_CASTLES" id="X_206_THE_KING_AND_THE_CASTLES"></a><a href="#X_206_THE_KING_AND_THE_CASTLESa"><b>206.—THE KING AND THE CASTLES.</b></a></p> + +<p>There was once, in ancient times, a powerful king, who had eccentric +ideas on the subject of military architecture. He held that there was +great strength and economy in symmetrical forms, and always cited the +example of the bees, who construct their combs in perfect hexagonal +cells, to prove that he had nature to support him. He resolved to +build ten new castles in his country all to be connected by fortified +walls, which should form five lines with four castles in every line. +The royal architect presented his preliminary plan in the form I have +shown. But the monarch pointed out that every castle could be +approached from the outside, and commanded that the plan should be so +modified that as many castles as possible should be free from attack +from the outside, and could only be reached by crossing the fortified +walls. The architect replied that he thought it impossible so to +arrange them that even one castle, which the king proposed to use as a +royal residence, could be so protected, but his majesty soon +enlightened him by pointing out how it might be done. How would you +have built the ten castles and fortifications so as best to fulfil the +king's requirements? Remember that they must form five straight lines +with four castles in every line.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q206.png" width="400" height="370" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_207_CHERRIES_AND_PLUMS" id="X_207_CHERRIES_AND_PLUMS"></a><a href="#X_207_CHERRIES_AND_PLUMSa"><b>207.—CHERRIES AND PLUMS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q207.png" width="400" height="400" alt="" title="" /> +</div> + +<p>The illustration is a plan of a cottage as it stands surrounded by an +orchard of fifty-five trees. Ten of these trees are cherries, ten are +plums, and the remainder apples. The cherries are so planted as to +form five straight lines, with four cherry trees in every line. The +plum trees <span class='pagenum'>Pg 57<a name="Page_57" id="Page_57"></a></span>are also planted so as to form five straight lines with +four plum trees in every line. The puzzle is to show which are the ten +cherry trees and which are the ten plums. In order that the cherries +and plums should have the most favourable aspect, as few as possible +(under the conditions) are planted on the north and east sides of the +orchard. Of course in picking out a group of ten trees (cherry or +plum, as the case may be) you ignore all intervening trees. That is to +say, four trees may be in a straight line irrespective of other trees +(or the house) being in between. After the last puzzle this will be +quite easy.</p> + +<hr style="width: 30%;" /> +<p><a name="X_208_A_PLANTATION_PUZZLE" id="X_208_A_PLANTATION_PUZZLE"></a><a href="#X_208_A_PLANTATION_PUZZLEa"><b>208.—A PLANTATION PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q208.png" width="400" height="405" alt="" title="" /> +</div> + +<p>A man had a square plantation of forty-nine trees, but, as will be +seen by the omissions in the illustration, four trees were blown down +and removed. He now wants to cut down all the remainder except ten +trees, which are to be so left that they shall form five straight rows +with four trees in every row. Which are the ten trees that he must +leave?</p> + +<hr style="width: 30%;" /> +<p><a name="X_209_THE_TWENTY-ONE_TREES" id="X_209_THE_TWENTY-ONE_TREES"></a><a href="#X_209_THE_TWENTY-ONE_TREESa"><b>209.—THE TWENTY-ONE TREES.</b></a></p> + +<p>A gentleman wished to plant twenty-one trees in his park so that they +should form twelve straight rows with five trees in every row. Could +you have supplied him with a pretty symmetrical arrangement that would +satisfy these conditions?</p> + +<hr style="width: 30%;" /> +<p><a name="X_210_THE_TEN_COINS" id="X_210_THE_TEN_COINS"></a><a href="#X_210_THE_TEN_COINSa"><b>210.—THE TEN COINS.</b></a></p> + +<p>Place ten pennies on a large sheet of paper or cardboard, as shown in +the diagram, five on each edge. Now remove four of the coins, without +disturbing the others, and replace them on the paper so that the ten +shall form five straight lines with four coins in every line. This in +itself is not difficult, but you should try to discover in how many +different ways the puzzle may be solved, assuming that in every case +the two rows at starting are exactly the same.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q210.png" width="400" height="394" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_211_THE_TWELVE_MINCE-PIES" id="X_211_THE_TWELVE_MINCE-PIES"></a><a href="#X_211_THE_TWELVE_MINCE-PIESa"><b>211.—THE TWELVE MINCE-PIES.</b></a></p> + +<p>It will be seen in our illustration how twelve mince-pies may be +placed on the table so as to form six straight rows with four pies in +every row. The puzzle is to remove only four of them to new positions +so that there shall be <i>seven</i> straight rows with four in every row. +Which four would you remove, and where would you replace them?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q211.png" width="400" height="509" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 58<a name="Page_58" id="Page_58"></a></span><a name="X_212_THE_BURMESE_PLANTATION" id="X_212_THE_BURMESE_PLANTATION"></a><a href="#X_212_THE_BURMESE_PLANTATIONa"><b>212.—THE BURMESE PLANTATION.</b></a></p> + +<p>A short time ago I received an interesting communication from the +British chaplain at Meiktila, Upper Burma, in which my correspondent +informed me that he had found some amusement on board ship on his way +out in trying to solve this little poser.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q212.png" width="400" height="398" alt="" title="" /> +</div> + +<p>If he has a plantation of forty-nine trees, planted in the form of a +square as shown in the accompanying illustration, he wishes to know +how he may cut down twenty-seven of the trees so that the twenty-two +left standing shall form as many rows as possible with four trees in +every row.</p> + +<p>Of course there may not be more than four trees in any row.</p> + +<hr style="width: 30%;" /> +<p><a name="X_213_TURKS_AND_RUSSIANS" id="X_213_TURKS_AND_RUSSIANS"></a><a href="#X_213_TURKS_AND_RUSSIANSa"><b>213.—TURKS AND RUSSIANS.</b></a></p> + +<p>This puzzle is on the lines of the Afridi problem published by me in +<i>Tit-Bits</i> some years ago.</p> + +<p>On an open level tract of country a party of Russian infantry, no two +of whom were stationed at the same spot, were suddenly surprised by +thirty-two Turks, who opened fire on the Russians from all directions. +Each of the Turks simultaneously fired a bullet, and each bullet +passed immediately over the heads of three Russian soldiers. As each +of these bullets when fired killed a different man, the puzzle is to +discover what is the smallest possible number of soldiers of which the +Russian party could have consisted and what were the casualties on +each side.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="MOVING_COUNTER_PROBLEMS" id="MOVING_COUNTER_PROBLEMS"></a><a href="#CONTENTS">MOVING COUNTER PROBLEMS.</a></h2> + + +<p class='center'> +"I cannot do't without counters."<br /> +<span style="margin-left: 8em;"><i>Winter's Tale</i>, iv. 3.<br /></span> +</p> + +<p>Puzzles of this class, except so far as they occur in connection with +actual games, such as chess, seem to be a comparatively modern +introduction. Mathematicians in recent times, notably Vandermonde and +Reiss, have devoted some attention to them, but they do not appear to +have been considered by the old writers. So far as games with counters +are concerned, perhaps the most ancient and widely known in old times +is "Nine Men's Morris" (known also, as I shall show, under a great +many other names), unless the simpler game, distinctly mentioned in +the works of Ovid (No. 110, "Ovid's Game," in <i>The Canterbury +Puzzles</i>), from which "Noughts and Crosses" seems to be derived, is +still more ancient.</p> + +<p>In France the game is called Marelle, in Poland Siegen Wulf Myll +(She-goat Wolf Mill, or Fight), in Germany and Austria it is called +Muhle (the Mill), in Iceland it goes by the name of Mylla, while the +Bogas (or native bargees) of South America are said to play it, and on +the Amazon it is called Trique, and held to be of Indian origin. In +our own country it has different names in different districts, such as +Meg Merrylegs, Peg Meryll, Nine Peg o'Merryal, Nine-Pin Miracle, Merry +Peg, and Merry Hole. Shakespeare refers to it in "Midsummer Night's +Dream" (Act ii., scene 1):—</p> + +<p> +<span style="margin-left: 2em;">"The nine-men's morris is filled up with mud;</span><br /> +<span style="margin-left: 2.5em;">And the quaint mazes in the wanton green,</span><br /> +<span style="margin-left: 2.5em;">For lack of tread, are undistinguishable."</span><br /> +</p> + +<p>It was played by the shepherds with stones in holes cut in the turf. +John Clare, the peasant poet of Northamptonshire, in "The Shepherd +Boy" (1835) says:—"Oft we track his haunts .... By nine-peg-morris +nicked upon the green." It is also mentioned by Drayton in his +"Polyolbion."</p> + +<p>It was found on an old Roman tile discovered during the excavations at +Silchester, and cut upon the steps of the Acropolis at Athens. When +visiting the Christiania Museum a few years ago I was shown the great +Viking ship that was discovered at Gokstad in 1880. On the oak planks +forming the deck of the vessel were found boles and lines marking out +the game, the holes being made to receive pegs. While inspecting the +ancient oak furniture in the Rijks Museum at Amsterdam I became +interested in an old catechumen's settle, and was surprised to find +the game diagram cut in the centre of the seat—quite conveniently for +surreptitious play. It has been discovered cut in the choir stalls of +several of our English cathedrals. In the early eighties it was found +scratched upon a stone built into a wall (probably about the date +1200), during the restoration of Hargrave church in Northamptonshire. +This stone is now in the Northampton Museum. A similar stone has since +been found at Sempringham, Lincolnshire. It is to be seen on an +ancient tombstone in the Isle of Man, and painted on old Dutch tiles. +And in 1901 a stone was dug out of a gravel pit near Oswestry bearing +an undoubted diagram of the game.</p> + +<p>The game has been played with different <span class='pagenum'>Pg 59<a name="Page_59" id="Page_59"></a></span>rules at different periods +and places. I give a copy of the board. Sometimes the diagonal lines +are omitted, but this evidently was not intended to affect the play: +it simply meant that the angles alone were thought sufficient to +indicate the points. This is how Strutt, in <i>Sports and Pastimes</i>, +describes the game, and it agrees with the way I played it as a +boy:—"Two persons, having each of them nine pieces, or men, lay them +down alternately, one by one, upon the spots; and the business of +either party is to prevent his antagonist from placing three of his +pieces so as to form a row of three, without the intervention of an +opponent piece. If a row be formed, he that made it is at liberty to +take up one of his competitor's pieces from any part he thinks most to +his advantage; excepting he has made a row, which must not be touched +if he have another piece upon the board that is not a component part +of that row. When all the pieces are laid down, they are played +backwards and forwards, in any direction that the lines run, but only +can move from one spot to another (next to it) at one time. He that +takes off all his antagonist's pieces is the conqueror."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/counter.png" width="400" height="393" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_214_THE_SIX_FROGS" id="X_214_THE_SIX_FROGS"></a><a href="#X_214_THE_SIX_FROGSa"><b>214.—THE SIX FROGS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q214.png" width="400" height="63" alt="" title="" /> +</div> + +<p>The six educated frogs in the illustration are trained to reverse +their order, so that their numbers shall read 6, 5, 4, 3, 2, 1, with +the blank square in its present position. They can jump to the next +square (if vacant) or leap over one frog to the next square beyond (if +vacant), just as we move in the game of draughts, and can go backwards +or forwards at pleasure. Can you show how they perform their feat in +the fewest possible moves? It is quite easy, so when you have done it +add a seventh frog to the right and try again. Then add more frogs +until you are able to give the shortest solution for any number. For +it can always be done, with that single vacant square, no matter how +many frogs there are.</p> + +<hr style="width: 30%;" /> +<p><a name="X_215_THE_GRASSHOPPER_PUZZLE" id="X_215_THE_GRASSHOPPER_PUZZLE"></a><a href="#X_215_THE_GRASSHOPPER_PUZZLEa"><b>215.—THE GRASSHOPPER PUZZLE.</b></a></p> + +<p>It has been suggested that this puzzle was a great favourite among the +young apprentices of the City of London in the sixteenth and +seventeenth centuries. Readers will have noticed the curious brass +grasshopper on the Royal Exchange. This long-lived creature escaped +the fires of 1666 and 1838. The grasshopper, after his kind, was the +crest of Sir Thomas Gresham, merchant grocer, who died in 1579, and +from this cause it has been used as a sign by grocers in general. +Unfortunately for the legend as to its origin, the puzzle was only +produced by myself so late as the year 1900. On twelve of the thirteen +black discs are placed numbered counters or grasshoppers. The puzzle +is to reverse their order, so that they shall read, 1, 2, 3, 4, etc., +in the opposite direction, with the vacant disc left in the same +position as at present. Move one at a time in any order, either to the +adjoining vacant disc or by jumping over one grasshopper, like the +moves in draughts. The moves or leaps may be made in either direction +that is at any time possible. What are the fewest possible moves in +which it can be done?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q215.png" width="400" height="399" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_216_THE_EDUCATED_FROGS" id="X_216_THE_EDUCATED_FROGS"></a><a href="#X_216_THE_EDUCATED_FROGSa"><b>216.—THE EDUCATED FROGS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q216.png" width="400" height="108" alt="" title="" /> +</div> + +<p>Our six educated frogs have learnt a new and pretty feat. When placed +on glass tumblers, as shown in the illustration, they change sides so +that the three black ones are to the left and the white frogs to the +right, with the unoccupied tumbler at the opposite end—No. 7. They +can jump to the next tumbler (if unoccupied), or over one, or two, +frogs to an unoccupied tumbler. The jumps can be made in either +direction, and a frog may jump over his own or the opposite colour, or +both colours. Four sue<span class='pagenum'>Pg 60<a name="Page_60" id="Page_60"></a></span>cessive specimen jumps will make everything +quite plain: 4 to 1, 5 to 4, 3 to 5, 6 to 3. Can you show how they do +it in ten jumps?</p> + +<hr style="width: 30%;" /> +<p><a name="X_217_THE_TWICKENHAM_PUZZLE" id="X_217_THE_TWICKENHAM_PUZZLE"></a><a href="#X_217_THE_TWICKENHAM_PUZZLEa"><b>217.—THE TWICKENHAM PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q217.png" width="400" height="406" alt="" title="" /> +</div> + +<p>In the illustration we have eleven discs in a circle. On five of the +discs we place white counters with black letters—as shown—and on +five other discs the black counters with white letters. The bottom +disc is left vacant. Starting thus, it is required to get the counters +into order so that they spell the word "Twickenham" in a clockwise +direction, leaving the vacant disc in the original position. The black +counters move in the direction that a clock-hand revolves, and the +white counters go the opposite way. A counter may jump over one of the +opposite colour if the vacant disc is next beyond. Thus, if your first +move is with K, then C can jump over K. If then K moves towards E, you +may next jump W over C, and so on. The puzzle may be solved in +twenty-six moves. Remember a counter cannot jump over one of its own +colour.</p> + +<hr style="width: 30%;" /> +<p><a name="X_218_THE_VICTORIA_CROSS_PUZZLE" id="X_218_THE_VICTORIA_CROSS_PUZZLE"></a><a href="#X_218_THE_VICTORIA_CROSS_PUZZLEa"><b>218.—THE VICTORIA CROSS PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q218.png" width="400" height="397" alt="" title="" /> +</div> + +<p>The puzzle-maker is peculiarly a "snapper-up of unconsidered trifles," +and his productions are often built up with the slenderest materials. +Trivialities that might entirely escape the observation of others, or, +if they were observed, would be regarded as of no possible moment, +often supply the man who is in quest of posers with a pretty theme or +an idea that he thinks possesses some "basal value."</p> + +<p>When seated opposite to a lady in a railway carriage at the time of +Queen Victoria's Diamond Jubilee, my attention was attracted to a +brooch that she was wearing. It was in the form of a Maltese or +Victoria Cross, and bore the letters of the word VICTORIA. The number +and arrangement of the letters immediately gave me the suggestion for +the puzzle which I now present.</p> + +<p>The diagram, it will be seen, is composed of nine divisions. The +puzzle is to place eight counters, bearing the letters of the word +VICTORIA, exactly in the manner shown, and then slide one letter at a +time from black to white and white to black alternately, until the +word reads round in the same direction, only with the initial letter V +on one of the black arms of the cross. At no time may two letters be +in the same division. It is required to find the shortest method.</p> + +<p>Leaping moves are, of course, not permitted. The first move must +obviously be made with A, I, T, or R. Supposing you move T to the +centre, the next counter played will be O or C, since I or R cannot be +moved. There is something a little remarkable in the solution of this +puzzle which I will explain.</p> + +<hr style="width: 30%;" /> +<p><a name="X_219_THE_LETTER_BLOCK_PUZZLE" id="X_219_THE_LETTER_BLOCK_PUZZLE"></a><a href="#X_219_THE_LETTER_BLOCK_PUZZLEa"><b>219.—THE LETTER BLOCK PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q219.png" width="400" height="404" alt="" title="" /> +</div> + +<p>Here is a little reminiscence of our old friend the Fifteen Block +Puzzle. Eight wooden blocks are lettered, and are placed in a box, as +shown in the illustration. It will be seen that you can only move one +block at a time to the place vacant for the time being, as no block +may be lifted out of the box. The puzzle is to shift them about until +you get them in the order—</p> + +<p><span class='pagenum'>Pg 61<a name="Page_61" id="Page_61"></a></span></p><p> +<span style="margin-left: 2em;">A B C</span><br /> +<span style="margin-left: 2em;">D E F</span><br /> +<span style="margin-left: 2em;">G H</span><br /> +</p> + +<p>This you will find by no means difficult if you are allowed as many +moves as you like. But the puzzle is to do it in the fewest possible +moves. I will not say what this smallest number of moves is, because +the reader may like to discover it for himself. In writing down your +moves you will find it necessary to record no more than the letters in +the order that they are shifted. Thus, your first five moves might be +C, H, G, E, F; and this notation can have no possible ambiguity. In +practice you only need eight counters and a simple diagram on a sheet +of paper.</p> + +<hr style="width: 30%;" /> +<p><a name="X_220_A_LODGING-HOUSE_DIFFICULTY" id="X_220_A_LODGING-HOUSE_DIFFICULTY"></a><a href="#X_220_A_LODGING-HOUSE_DIFFICULTYa"><b>220.—A LODGING-HOUSE DIFFICULTY.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q220.png" width="400" height="268" alt="" title="" /> +</div> + +<p>The Dobsons secured apartments at Slocomb-on-Sea. There were six rooms +on the same floor, all communicating, as shown in the diagram. The +rooms they took were numbers 4, 5, and 6, all facing the sea. But a +little difficulty arose. Mr. Dobson insisted that the piano and the +bookcase should change rooms. This was wily, for the Dobsons were not +musical, but they wanted to prevent any one else playing the +instrument. Now, the rooms were very small and the pieces of furniture +indicated were very big, so that no two of these articles could be got +into any room at the same time. How was the exchange to be made with +the least possible labour? Suppose, for example, you first move the +wardrobe into No. 2; then you can move the bookcase to No. 5 and the +piano to No. 6, and so on. It is a fascinating puzzle, but the +landlady had reasons for not appreciating it. Try to solve her +difficulty in the fewest possible removals with counters on a sheet of +paper.</p> + +<hr style="width: 30%;" /> +<p><a name="X_221_THE_EIGHT_ENGINES" id="X_221_THE_EIGHT_ENGINES"></a><a href="#X_221_THE_EIGHT_ENGINESa"><b>221.—THE EIGHT ENGINES.</b></a></p> + +<p>The diagram represents the engine-yard of a railway company under +eccentric management. The engines are allowed to be stationary only at +the nine points indicated, one of which is at present vacant. It is +required to move the engines, one at a time, from point to point, in +seventeen moves, so that their numbers shall be in numerical order +round the circle, with the central point left vacant. But one of the +engines has had its fire drawn, and therefore cannot move. How is the +thing to be done? And which engine remains stationary throughout?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q221.png" width="400" height="425" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_222_A_RAILWAY_PUZZLE" id="X_222_A_RAILWAY_PUZZLE"></a><a href="#X_222_A_RAILWAY_PUZZLEa"><b>222.—A RAILWAY PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q222.png" width="400" height="482" alt="" title="" /> +</div> + +<p>Make a diagram, on a large sheet of paper, like the illustration, and +have three counters marked A, three marked B, and three marked C. It +will be seen that at the intersection of lines there are nine +stopping-places, and a tenth stopping-<span class='pagenum'>Pg 62<a name="Page_62" id="Page_62"></a></span>place is attached to the outer +circle like the tail of a Q. Place the three counters or engines +marked A, the three marked B, and the three marked C at the places +indicated. The puzzle is to move the engines, one at a time, along the +lines, from stopping-place to stopping-place, until you succeed in +getting an A, a B, and a C on each circle, and also A, B, and C on +each straight line. You are required to do this in as few moves as +possible. How many moves do you need?</p> + +<hr style="width: 30%;" /> +<p><a name="X_223_A_RAILWAY_MUDDLE" id="X_223_A_RAILWAY_MUDDLE"></a><a href="#X_223_A_RAILWAY_MUDDLEa"><b>223.—A RAILWAY MUDDLE.</b></a></p> + +<p>The plan represents a portion of the line of the London, Clodville, +and Mudford Railway Company. It is a single line with a loop. There is +only room for eight wagons, or seven wagons and an engine, between B +and C on either the left line or the right line of the loop. It +happened that two goods trains (each consisting of an engine and +sixteen wagons) got into the position shown in the illustration. It +looked like a hopeless deadlock, and each engine-driver wanted the +other to go back to the next station and take off nine wagons. But an +ingenious stoker undertook to pass the trains and send them on their +respective journeys with their engines properly in front. He also +contrived to reverse the engines the fewest times possible. Could you +have performed the feat? And how many times would you require to +reverse the engines? A "reversal" means a change of direction, +backward or forward. No rope-shunting, fly-shunting, or other trick is +allowed. All the work must be done legitimately by the two engines. It +is a simple but interesting puzzle if attempted with counters.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q223.png" width="400" height="638" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_224_THE_MOTOR-GARAGE_PUZZLE" id="X_224_THE_MOTOR-GARAGE_PUZZLE"></a><a href="#X_224_THE_MOTOR-GARAGE_PUZZLEa"><b>224.—THE MOTOR-GARAGE PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q224.png" width="400" height="491" alt="" title="" /> +</div> + +<p>The difficulties of the proprietor of a motor garage are converted +into a little pastime of a kind that has a peculiar fascination. All +you need is to make a simple plan or diagram on a sheet of paper or +cardboard and number eight counters, 1 to 8. Then a whole family can +enter into an amusing competition to find the best possible solution +of the difficulty.</p> + +<p>The illustration represents the plan of a motor garage, with +accommodation for twelve cars. But the premises are so inconveniently +restricted that the proprietor is often caused considerable +perplexity. Suppose, for example, that the eight cars numbered 1 to 8 +are in the positions shown, how are they to be shifted in the quickest +possible way so that 1, 2, 3, and 4 shall change places with 5, 6, 7, +and 8—that is, with the numbers still running from left to right, as +at present, but the top row exchanged with the bottom row? What are +the fewest possible moves?</p> + +<p>One car moves at a time, and any distance counts as one move. To +prevent misunderstanding, the stopping-places are marked in squares, +and only one car can be in a square at the same time.</p> + +<hr style="width: 30%;" /> +<p><a name="X_225_THE_TEN_PRISONERS" id="X_225_THE_TEN_PRISONERS"></a><a href="#X_225_THE_TEN_PRISONERSa"><b>225.—THE TEN PRISONERS.</b></a></p> + +<p>If prisons had no other use, they might still be preserved for the +special benefit of puzzle-makers. They appear to be an inexhaustible +mine of perplexing ideas. Here is a little poser that will perhaps +interest the reader for a short period. We have in the illustration a +prison of sixteen cells. The locations of the ten prisoners will be +seen. The jailer has queer superstitions about odd and even numbers, +and he <span class='pagenum'>Pg 63<a name="Page_63" id="Page_63"></a></span>wants to rearrange the ten prisoners so that there shall be as +many even rows of men, vertically, horizontally, and diagonally, as +possible. At present it will be seen, as indicated by the arrows, that +there are only twelve such rows of 2 and 4. I will state at once that +the greatest number of such rows that is possible is sixteen. But the +jailer only allows four men to be removed to other cells, and informs +me that, as the man who is seated in the bottom right-hand corner is +infirm, he must not be moved. Now, how are we to get those sixteen +rows of even numbers under such conditions?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q225.png" width="400" height="392" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_226_ROUND_THE_COAST" id="X_226_ROUND_THE_COAST"></a><a href="#X_226_ROUND_THE_COASTa"><b>226.—ROUND THE COAST.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q226.png" width="400" height="398" alt="" title="" /> +</div> + +<p>Here is a puzzle that will, I think, be found as amusing as +instructive. We are given a ring of eight circles. Leaving circle 8 +blank, we are required to write in the name of a seven-lettered port +in the United Kingdom in this manner. Touch a blank circle with your +pencil, then jump over two circles in either direction round the ring, +and write down the first letter. Then touch another vacant circle, +jump over two circles, and write down your second letter. Proceed +similarly with the other letters in their proper order until you have +completed the word. Thus, suppose we select "Glasgow," and proceed as +follows: 6—1, 7—2, 8—3, 7—4, 8—5, which means that we touch 6, +jump over 7 and and write down "G" on 1; then touch 7, jump over 8 and +1, and write down "l" on 2; and so on. It will be found that after we +have written down the first five letters—"Glasg"—as above, we cannot +go any further. Either there is something wrong with "Glasgow," or we +have not managed our jumps properly. Can you get to the bottom of the +mystery?</p> + +<hr style="width: 30%;" /> +<p><a name="X_227_CENTRAL_SOLITAIRE" id="X_227_CENTRAL_SOLITAIRE"></a><a href="#X_227_CENTRAL_SOLITAIREa"><b>227.—CENTRAL SOLITAIRE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q227.png" width="400" height="397" alt="" title="" /> +</div> + +<p>This ancient puzzle was a great favourite with our grandmothers, and +most of us, I imagine, have on occasions come across a "Solitaire" +board—a round polished board with holes cut in it in a geometrical +pattern, and a glass marble in every hole. Sometimes I have noticed +one on a side table in a suburban front parlour, or found one on a +shelf in a country cottage, or had one brought under my notice at a +wayside inn. Sometimes they are of the form shown above, but it is +equally common for the board to have four more holes, at the points +indicated by dots. I select the simpler form.</p> + +<p>Though "Solitaire" boards are still sold at the toy shops, it will be +sufficient if the reader will make an enlarged copy of the above on a +sheet of cardboard or paper, number the "holes," and provide himself +with 33 counters, buttons, or beans. Now place a counter in every hole +except the central one, No. 17, and the puzzle is to take off all the +counters in a series of jumps, except the last counter, which must be +left in that central hole. You are <span class='pagenum'>Pg 64<a name="Page_64" id="Page_64"></a></span>allowed to jump one counter over +the next one to a vacant hole beyond, just as in the game of draughts, +and the counter jumped over is immediately taken off the board. Only +remember every move must be a jump; consequently you will take off a +counter at each move, and thirty-one single jumps will of course +remove all the thirty-one counters. But compound moves are allowed (as +in draughts, again), for so long as one counter continues to jump, the +jumps all count as one move.</p> + +<p>Here is the beginning of an imaginary solution which will serve to +make the manner of moving perfectly plain, and show how the solver +should write out his attempts: 5-17, 12-10, 26-12, 24-26 (13-11, +11-25), 9-11 (26-24, 24-10, 10-12), etc., etc. The jumps contained +within brackets count as one move, because they are made with the same +counter. Find the fewest possible moves. Of course, no diagonal jumps +are permitted; you can only jump in the direction of the lines.</p> + +<hr style="width: 30%;" /> +<p><a name="X_228_THE_TEN_APPLES" id="X_228_THE_TEN_APPLES"></a><a href="#X_228_THE_TEN_APPLESa"><b>228.—THE TEN APPLES.</b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q228.png" width="600" height="425" alt="" title="" /> +</div> + +<p>The family represented in the illustration are amusing themselves with +this little puzzle, which is not very difficult but quite interesting. +They have, it will be seen, placed sixteen plates on the table in the +form of a square, and put an apple in each of ten plates. They want to +find a way of removing all the apples except one by jumping over one +at a time to the next vacant square, as in draughts; or, better, as in +solitaire, for you are not allowed to make any diagonal moves—only +moves parallel to the sides of the square. It is obvious that as the +apples stand no move can be made, but you are permitted to transfer +any single apple you like to a vacant plate before starting. Then the +moves must be all leaps, taking off the apples leaped over.</p> + +<hr style="width: 30%;" /> +<p><a name="X_229_THE_NINE_ALMONDS" id="X_229_THE_NINE_ALMONDS"></a><a href="#X_229_THE_NINE_ALMONDSa"><b>229.—THE NINE ALMONDS.</b></a></p> + +<p>"Here is a little puzzle," said a Parson, "that I have found +peculiarly fascinating. It is so simple, and yet it keeps you +interested indefinitely."</p> + +<p>The reverend gentleman took a sheet of paper and divided it off into +twenty-five squares, like a square portion of a chessboard. Then he +placed nine almonds on the central squares, as shown in the +illustration, where we have represented numbered counters for +convenience in giving the solution.</p> + +<p>"Now, the puzzle is," continued the Parson, "to remove eight of the +almonds and leave the ninth in the central square. You make the +removals by jumping one almond over another to the vacant square +beyond and taking off the one jumped over—just as in draughts, only +here you can jump in any direction, and not diagonally only. The point +is to do the thing in the fewest possible moves."</p> + +<p>The following specimen attempt will make everything clear. Jump 4 over +1, 5 over 9, 3 over 6, 5 over 3, 7 over 5 and 2, 4 over 7, 8 over 4. +But 8 is not left in the central square, as it <span class='pagenum'>Pg 65<a name="Page_65" id="Page_65"></a></span>should be. Remember to +remove those you jump over. Any number of jumps in succession with the +same almond count as one move.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q229.png" width="400" height="399" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_230_THE_TWELVE_PENNIES" id="X_230_THE_TWELVE_PENNIES"></a><a href="#X_230_THE_TWELVE_PENNIESa"><b>230.—THE TWELVE PENNIES.</b></a></p> + +<p>Here is a pretty little puzzle that only requires twelve pennies or +counters. Arrange them in a circle, as shown in the illustration. Now +take up one penny at a time and, passing it over two pennies, place it +on the third penny. Then take up another single penny and do the same +thing, and so on, until, in six such moves, you have the coins in six +pairs in the positions 1, 2, 3, 4, 5, 6. You can move in either +direction round the circle at every play, and it does not matter +whether the two jumped over are separate or a pair. This is quite easy +if you use just a little thought.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q230.png" width="400" height="401" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_231_PLATES_AND_COINS" id="X_231_PLATES_AND_COINS"></a><a href="#X_231_PLATES_AND_COINSa"><b>231.—PLATES AND COINS.</b></a></p> + +<p>Place twelve plates, as shown, on a round table, with a penny or +orange in every plate. Start from any plate you like and, always going +in one direction round the table, take up one penny, pass it over two +other pennies, and place it in the next plate. Go on again; take up +another penny and, having passed it over two pennies, place it in a +plate; and so continue your journey. Six coins only are to be removed, +and when these have been placed there should be two coins in each of +six plates and six plates empty. An important point of the puzzle is +to go round the table as few times as possible. It does not matter +whether the two coins passed over are in one or two plates, nor how +many empty plates you pass a coin over. But you must always go in one +direction round the table and end at the point from which you set out. +Your hand, that is to say, goes steadily forward in one direction, +without ever moving backwards.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q231.png" width="400" height="288" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_232_CATCHING_THE_MICE" id="X_232_CATCHING_THE_MICE"></a><a href="#X_232_CATCHING_THE_MICEa"><b>232.—CATCHING THE MICE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q232.png" width="400" height="408" alt="" title="" /> +</div> + +<p>"Play fair!" said the mice. "You know the rules of the game."</p> + +<p>"Yes, I know the rules," said the cat. "I've got to go round and round +the circle, in the <span class='pagenum'>Pg 66<a name="Page_66" id="Page_66"></a></span>direction that you are looking, and eat every +thirteenth mouse, but I must keep the white mouse for a tit-bit at the +finish. Thirteen is an unlucky number, but I will do my best to oblige +you."</p> + +<p>"Hurry up, then!" shouted the mice.</p> + +<p>"Give a fellow time to think," said the cat. "I don't know which of +you to start at. I must figure it out."</p> + +<p>While the cat was working out the puzzle he fell asleep, and, the +spell being thus broken, the mice returned home in safety. At which +mouse should the cat have started the count in order that the white +mouse should be the last eaten?</p> + +<p>When the reader has solved that little puzzle, here is a second one +for him. What is the smallest number that the cat can count round and +round the circle, if he must start at the white mouse (calling that +"one" in the count) and still eat the white mouse last of all?</p> + +<p>And as a third puzzle try to discover what is the smallest number that +the cat can count round and round if she must start at the white mouse +(calling that "one") and make the white mouse the third eaten.</p> + +<hr style="width: 30%;" /> +<p><a name="X_233_THE_ECCENTRIC_CHEESEMONGER" id="X_233_THE_ECCENTRIC_CHEESEMONGER"></a><a href="#X_233_THE_ECCENTRIC_CHEESEMONGERa"><b>233.—THE ECCENTRIC CHEESEMONGER.</b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q233.png" width="600" height="516" alt="" title="" /> +</div> + +<p>The cheesemonger depicted in the illustration is an inveterate puzzle +lover. One of his favourite puzzles is the piling of cheeses in his +warehouse, an amusement that he finds good exercise for the body as +well as for the mind. He places sixteen cheeses on the floor in a +straight row and then makes them into four piles, with four cheeses in +every pile, by always passing a cheese over four others. If you use +sixteen counters and number them in order from 1 to 16, then you may +place 1 on 6, 11 on 1, 7 on 4, and so on, until there are four in +every pile. It will be seen that it does not matter whether the four +passed over are standing alone or piled; they count just the same, and +you can always carry a cheese in either direction. There are a great +many different ways of doing it in twelve moves, so it makes a good +game of "patience" to try to solve it so that the four piles shall be +left in different stipulated places. For example, try to leave the +piles at the extreme ends of the row, on Nos. 1, 2, 15 and 16; this is +quite easy. Then try to leave three piles together, on Nos. 13, 14, +and 15. Then again play so that they shall be left on Nos. 3, 5, 12, +and 14.</p> + +<hr style="width: 30%;" /> +<p><a name="X_234_THE_EXCHANGE_PUZZLE" id="X_234_THE_EXCHANGE_PUZZLE"></a><a href="#X_234_THE_EXCHANGE_PUZZLEa"><b>234.—THE EXCHANGE PUZZLE.</b></a></p> + + +<p>Here is a rather entertaining little puzzle with moving counters. You +only need twelve counters—six of one colour, marked A, C, E, G, I, +and K, and the other six marked B, D, F, H, J, and L. You first place +them on the diagram, as shown in the illustration, and the puzzle is +to get them into regular alphabetical order, as follows:—<span class='pagenum'>Pg 67<a name="Page_67" id="Page_67"></a></span></p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>A</td><td align='center'>B</td><td align='center'>C</td><td align='center'>D</td></tr> +<tr><td align='center'>E</td><td align='center'>F</td><td align='center'>G</td><td align='center'>H</td></tr> +<tr><td align='center'>I</td><td align='center'>J</td><td align='center'>K</td><td align='center'>L</td></tr> +</table></div> + +<p>The moves are made by exchanges of opposite colours standing on the +same line. Thus, G and J may exchange places, or F and A, but you +cannot exchange G and C, or F and D, because in one case they are both +white and in the other case both black. Can you bring about the +required arrangement in seventeen exchanges?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q234.png" width="400" height="282" alt="" title="" /> +</div> + +<p>It cannot be done in fewer moves. The puzzle is really much easier +than it looks, if properly attacked.</p> + +<hr style="width: 30%;" /> +<p><a name="X_235_TORPEDO_PRACTICE" id="X_235_TORPEDO_PRACTICE"></a><a href="#X_235_TORPEDO_PRACTICEa"><b>235.—TORPEDO PRACTICE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q235.png" width="400" height="405" alt="" title="" /> +</div> + +<p>If a fleet of sixteen men-of-war were lying at anchor and surrounded +by the enemy, how many ships might be sunk if every torpedo, projected +in a straight line, passed under three vessels and sank the fourth? In +the diagram we have arranged the fleet in square formation, where it +will be seen that as many as seven ships may be sunk (those in the top +row and first column) by firing the torpedoes indicated by arrows. +Anchoring the fleet as we like, to what extent can we increase this +number? Remember that each successive ship is sunk before another +torpedo is launched, and that every torpedo proceeds in a different +direction; otherwise, by placing the ships in a straight line, we +might sink as many as thirteen! It is an interesting little study in +naval warfare, and eminently practical—provided the enemy will allow +you to arrange his fleet for your convenience and promise to lie still +and do nothing!</p> + +<hr style="width: 30%;" /> +<p><a name="X_236_THE_HAT_PUZZLE" id="X_236_THE_HAT_PUZZLE"></a><a href="#X_236_THE_HAT_PUZZLEa"><b>236.—THE HAT PUZZLE.</b></a></p> + +<p>Ten hats were hung on pegs as shown in the illustration—five silk +hats and five felt "bowlers," alternately silk and felt. The two pegs +at the end of the row were empty.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q236.png" width="600" height="61" alt="" title="" /> +</div> + +<p>The puzzle is to remove two contiguous hats to the vacant pegs, then +two other adjoining hats to the pegs now unoccupied, and so on until +five pairs have been moved and the hats again hang in an unbroken row, +but with all the silk ones together and all the felt hats together.</p> + +<p>Remember, the two hats removed must always be contiguous ones, and you +must take one in each hand and place them on their new pegs without +reversing their relative position. You are not allowed to cross your +hands, nor to hang up one at a time.</p> + +<p>Can you solve this old puzzle, which I give as introductory to the +next? Try it with counters of two colours or with coins, and remember +that the two empty pegs must be left at one end of the row.</p> + +<hr style="width: 30%;" /> +<p><a name="X_237_BOYS_AND_GIRLS" id="X_237_BOYS_AND_GIRLS"></a><a href="#X_237_BOYS_AND_GIRLSa"><b>237.—BOYS AND GIRLS.</b></a></p> + +<p>If you mark off ten divisions on a sheet of paper to represent the +chairs, and use eight numbered counters for the children, you will +have a fascinating pastime. Let the odd numbers represent boys and +even numbers girls, or you can use counters of two colours, or coins.</p> + +<p>The puzzle is to remove two children who are occupying adjoining +chairs and place them in two empty chairs, <i>making them first change +sides</i>; then remove a second pair of children from adjoining chairs +and place them in the two now vacant, making them change sides; and so +on, until all the boys are together and all the girls together, with +the two vacant chairs at one end as at present. To solve the puzzle +you must do this in five moves. The two children must always be taken +from chairs that are next to one another; and remember the important +point of making the two children change sides, <span class='pagenum'>Pg 68<a name="Page_68" id="Page_68"></a></span>as this latter is the +distinctive feature of the puzzle. By "change sides" I simply mean +that if, for example, you first move 1 and 2 to the vacant chairs, +then the first (the outside) chair will be occupied by 2 and the +second one by 1.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q237.png" width="600" height="148" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_238_ARRANGING_THE_JAMPOTS" id="X_238_ARRANGING_THE_JAMPOTS"></a><a href="#X_238_ARRANGING_THE_JAMPOTSa"><b>238.—ARRANGING THE JAMPOTS.</b></a></p> + +<p>I happened to see a little girl sorting out some jam in a cupboard for +her mother. She was putting each different kind of preserve apart on +the shelves. I noticed that she took a pot of damson in one hand and a +pot of gooseberry in the other and made them change places; then she +changed a strawberry with a raspberry, and so on. It was interesting +to observe what a lot of unnecessary trouble she gave herself by +making more interchanges than there was any need for, and I thought it +would work into a good puzzle.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q238.png" width="600" height="500" alt="" title="" /> +</div> + +<p>It will be seen in the illustration that little Dorothy has to +manipulate twenty-four large jampots in as many pigeon-holes. She +wants to get them in correct numerical order—that is, 1, 2, 3, 4, 5, +6 on the top shelf, 7, 8, 9, 10, 11, 12 on the next shelf, and so on. +Now, if she always takes one pot in the right hand and another in the +left and makes them change places, how many of these interchanges will +be necessary to get all the jampots in proper order? She would +naturally first change the 1 and the 3, then the 2 and the 3, when she +would have the first three pots in their places. How would you advise +her to go on then? Place some numbered counters on a sheet of paper +divided into squares for the pigeon-holes, and you will find it an +amusing puzzle.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="UNICURSAL_AND_ROUTE_PROBLEMS" id="UNICURSAL_AND_ROUTE_PROBLEMS"></a><a href="#CONTENTS">UNICURSAL AND ROUTE PROBLEMS.</a></h2> + +<p class='center'> +"I see them on their winding way."<br /> +<span style="margin-left: 8em;">REGINALD HEBER.</span><br /> +</p> + +<p>It is reasonable to suppose that from the earliest ages one man has +asked another such questions as these: "Which is the nearest way +home?" "Which is the easiest or pleasantest way?" "How can we find a +way that will enable us to dodge the mastodon and the plesiosaurus?" +"How can we get there without ever crossing the track of the enemy?" +All these are elementary route problems, and they can be turned into +good puzzles by the introduction of some conditions that complicate +matters. A variety of such complications will be found in the +following examples. I have also included some enumerations of more or +less difficulty. These afford excellent practice for the reasoning +faculties, and enable one to generalize in the case of symmetrical +forms in a manner that is most instructive.</p> + +<hr style="width: 30%;" /> +<p><a name="X_239_A_JUVENILE_PUZZLE" id="X_239_A_JUVENILE_PUZZLE"></a><a href="#X_239_A_JUVENILE_PUZZLEa"><b>239.—A JUVENILE PUZZLE.</b></a></p> + +<p>For years I have been perpetually consulted by my juvenile friends +about this little puzzle. Most children seem to know it, and yet, +curiously enough, they are invariably unacquainted with the answer. +The question they always ask is, "Do, please, tell me whether it is +really possible." I believe Houdin the conjurer used to be very fond +of giving it to his child friends, but I cannot say whether he +invented the little puzzle or not. No doubt a large number of my +readers will be glad to have the mystery of the solution cleared up, +so I make no apology for introducing this old "teaser."</p> + +<p>The puzzle is to draw with three strokes of the pencil the diagram +that the little girl is exhibiting in the illustration. Of course, you +must not remove your pencil from the paper during a stroke or go over +the same line a second time. You will find that you can get <span class='pagenum'>Pg 69<a name="Page_69" id="Page_69"></a></span>in a good +deal of the figure with one continuous stroke, but it will always +appear as if four strokes are necessary.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q239.png" width="400" height="380" alt="" title="" /> +</div> + +<p>Another form of the puzzle is to draw the diagram on a slate and then +rub it out in three rubs.</p> + +<hr style="width: 30%;" /> +<p><a name="X_240_THE_UNION_JACK" id="X_240_THE_UNION_JACK"></a><a href="#X_240_THE_UNION_JACKa"><b>240.—THE UNION JACK.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q240.png" width="400" height="287" alt="" title="" /> +</div> + +<p>The illustration is a rough sketch somewhat resembling the British +flag, the Union Jack. It is not possible to draw the whole of it +without lifting the pencil from the paper or going over the same line +twice. The puzzle is to find out just <i>how much</i> of the drawing it is +possible to make without lifting your pencil or going twice over the +same line. Take your pencil and see what is the best you can do.</p> + +<hr style="width: 30%;" /> +<p><a name="X_241_THE_DISSECTED_CIRCLE" id="X_241_THE_DISSECTED_CIRCLE"></a><a href="#X_241_THE_DISSECTED_CIRCLEa"><b>241.—THE DISSECTED CIRCLE.</b></a></p> + +<p>How many continuous strokes, without lifting your pencil from the +paper, do you require to draw the design shown in our illustration? +Directly you change the direction of your pencil it begins a new +stroke. You may go over the same line more than once if you like. It +requires just a little care, or you may find yourself beaten by one +stroke.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q241.png" width="400" height="392" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_242_THE_TUBE_INSPECTORS_PUZZLE" id="X_242_THE_TUBE_INSPECTORS_PUZZLE"></a><a href="#X_242_THE_TUBE_INSPECTORS_PUZZLEa"><b>242.—THE TUBE INSPECTOR'S PUZZLE.</b></a></p> + +<p>The man in our illustration is in a little dilemma. He has just been +appointed inspector of a certain system of tube railways, and it is +his duty to inspect regularly, within a stated period, all the +company's seventeen lines connecting twelve stations, as shown on the +big poster plan that he is contemplating. Now he wants to arrange his +route so that it shall take him over all the lines with as little +travelling as possible. He may begin where he likes and end where he +likes. What is his shortest route?</p> + +<p>Could anything be simpler? But the reader will soon find that, however +he decides to proceed, the inspector must go over some of the lines +more than once. In other words, if we say that the stations are a mile +apart, he will have to travel more than seventeen miles to inspect +every line. There is the little difficulty. How far is he compelled to +travel, and which route do you recommend?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q242.png" width="400" height="461" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 70<a name="Page_70" id="Page_70"></a></span><a name="X_243_VISITING_THE_TOWNS" id="X_243_VISITING_THE_TOWNS"></a><a href="#X_243_VISITING_THE_TOWNSa"><b>243.—VISITING THE TOWNS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q243.png" width="400" height="251" alt="" title="" /> +</div> + +<p>A traveller, starting from town No. 1, wishes to visit every one of +the towns once, and once only, going only by roads indicated by +straight lines. How many different routes are there from which he can +select? Of course, he must end his journey at No. 1, from which he +started, and must take no notice of cross roads, but go straight from +town to town. This is an absurdly easy puzzle, if you go the right way +to work.</p> + +<hr style="width: 30%;" /> +<p><a name="X_244_THE_FIFTEEN_TURNINGS" id="X_244_THE_FIFTEEN_TURNINGS"></a><a href="#X_244_THE_FIFTEEN_TURNINGSa"><b>244.—THE FIFTEEN TURNINGS.</b></a></p> + +<p>Here is another queer travelling puzzle, the solution of which calls +for ingenuity. In this case the traveller starts from the black town +and wishes to go as far as possible while making only fifteen turnings +and never going along the same road twice. The towns are supposed to +be a mile apart. Supposing, for example, that he went straight to A, +then straight to B, then to C, D, E, and F, you will then find that he +has travelled thirty-seven miles in five turnings. Now, how far can he +go in fifteen turnings?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q244.png" width="400" height="384" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_245_THE_FLY_ON_THE_OCTAHEDRON" id="X_245_THE_FLY_ON_THE_OCTAHEDRON"></a><a href="#X_245_THE_FLY_ON_THE_OCTAHEDRONa"><b>245.—THE FLY ON THE OCTAHEDRON.</b></a></p> + +<p>"Look here," said the professor to his colleague, "I have been +watching that fly on the octahedron, and it confines its walks +entirely to the edges. What can be its reason for avoiding the sides?"</p> + +<p>"Perhaps it is trying to solve some route problem," suggested the +other. "Supposing it to start from the top point, how many different +routes are there by which it may walk over all the edges, without ever +going twice along the same edge in any route?"</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q245.png" width="400" height="528" alt="" title="" /> +</div> + +<p>The problem was a harder one than they expected, and after working at +it during leisure moments for several days their results did not +agree—in fact, they were both wrong. If the reader is surprised at +their failure, let him attempt the little puzzle himself. I will just +explain that the octahedron is one of the five regular, or Platonic, +bodies, and is contained under eight equal and equilateral triangles. +If you cut out the two pieces of cardboard of the shape shown in the +margin of the illustration, cut half through along the dotted lines +and then bend them and put them together, you will have a perfect +octahedron. In any route over all the edges it will be found that the +fly must end at the point of departure at the top.</p> + +<hr style="width: 30%;" /> +<p><a name="X_246_THE_ICOSAHEDRON_PUZZLE" id="X_246_THE_ICOSAHEDRON_PUZZLE"></a><a href="#X_246_THE_ICOSAHEDRON_PUZZLEa"><b>246.—THE ICOSAHEDRON PUZZLE.</b></a></p> + +<p>The icosahedron is another of the five regular, or Platonic, bodies +having all their sides, angles, and planes similar and equal. It is +bounded by twenty similar equilateral triangles. If you cut out a +piece of cardboard of the form shown in the smaller diagram, and cut +half through along the dotted lines, it will fold up and form a +perfect icosahedron.</p> + +<p>Now, a Platonic body does not mean a <span class='pagenum'>Pg 71<a name="Page_71" id="Page_71"></a></span>heavenly body; but it will suit +the purpose of our puzzle if we suppose there to be a habitable planet +of this shape. We will also suppose that, owing to a superfluity of +water, the only dry land is along the edges, and that the inhabitants +have no knowledge of navigation. If every one of those edges is 10,000 +miles long and a solitary traveller is placed at the North Pole (the +highest point shown), how far will he have to travel before he will +have visited every habitable part of the planet—that is, have +traversed every one of the edges?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q246.png" width="400" height="652" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_247_INSPECTING_A_MINE" id="X_247_INSPECTING_A_MINE"></a><a href="#X_247_INSPECTING_A_MINEa"><b>247.—INSPECTING A MINE.</b></a></p> + +<p>The diagram is supposed to represent the passages or galleries in a +mine. We will assume that every passage, A to B, B to C, C to H, H to +I, and so on, is one furlong in length. It will be seen that there are +thirty-one of these passages. Now, an official has to inspect all of +them, and he descends by the shaft to the point A. How far must he +travel, and what route do you recommend? The reader may at first say, +"As there are thirty-one passages, each a furlong in length, he will +have to travel just thirty-one furlongs." But this is assuming that he +need never go along a passage more than once, which is not the case. +Take your pencil and try to find the shortest route. You will soon +discover that there is room for considerable judgment. In fact, it is +a perplexing puzzle.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q247.png" width="400" height="310" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_248_THE_CYCLISTS_TOUR" id="X_248_THE_CYCLISTS_TOUR"></a><a href="#X_248_THE_CYCLISTS_TOURa"><b>248.—THE CYCLISTS' TOUR.</b></a></p> + +<p>Two cyclists were consulting a road map in preparation for a little +tour together. The circles represent towns, and all the good roads are +represented by lines. They are starting from the town with a star, and +must complete their tour at E. But before arriving there they want to +visit every other town once, and only once. That is the difficulty. +Mr. Spicer said, "I am certain we can find a way of doing it;" but Mr. +Maggs replied, "No way, I'm sure." Now, which of them was correct? +Take your pencil and see if you can find any way of doing it. Of +course you must keep to the roads indicated.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q248.png" width="400" height="318" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_249_THE_SAILORS_PUZZLE" id="X_249_THE_SAILORS_PUZZLE"></a><a href="#X_249_THE_SAILORS_PUZZLEa"><b>249.—THE SAILOR'S PUZZLE.</b></a></p> + +<p>The sailor depicted in the illustration stated that he had since his +boyhood been engaged in trading with a small vessel among some twenty +little islands in the Pacific. He supplied the rough chart of which I +have given a copy, and explained that the lines from island to island +represented the only routes that he ever adopted. He always started +from island A at the beginning of the season, and then visited every +island <span class='pagenum'>Pg 72<a name="Page_72" id="Page_72"></a></span>once, and once only, finishing up his tour at the +starting-point A. But he always put off his visit to C as long as +possible, for trade reasons that I need not enter into. The puzzle is +to discover his exact route, and this can be done with certainty. Take +your pencil and, starting at A, try to trace it out. If you write down +the islands in the order in which you visit them—thus, for example, +A, I, O, L, G, etc.—you can at once see if you have visited an island +twice or omitted any. Of course, the crossings of the lines must be +ignored—that is, you must continue your route direct, and you are not +allowed to switch off at a crossing and proceed in another direction. +There is no trick of this kind in the puzzle. The sailor knew the best +route. Can you find it?</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q249.png" width="600" height="777" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_250_THE_GRAND_TOUR" id="X_250_THE_GRAND_TOUR"></a><a href="#X_250_THE_GRAND_TOURa"><b>250.—THE GRAND TOUR.</b></a></p> + +<p>One of the everyday puzzles of life is the working out of routes. If +you are taking a holiday on your bicycle, or a motor tour, there +always arises the question of how you are to make the best of your +time and other resources. You have determined to get as far as some +particular place, to include visits to such-and-such a town, to try to +see something of special interest elsewhere, and perhaps to try to +look up an old friend at a spot that will not take you much out of +your way. Then you have to plan your route so as to avoid bad roads, +uninteresting country, and, if possible, the necessity of a return by +the same way that you went. With a map before you, the interesting +puzzle is attacked and solved. I will present a little poser based on +these lines.</p> + +<p>I give a rough map of a country—it is not necessary to say what +particular country—the circles representing towns and the dotted +lines the railways connecting them. Now there lived in the town marked +A a man who was born there, and during the whole of his life had never +once left his native place. From his youth upwards he had been very +industrious, sticking incessantly to his trade, and had no desire +whatever to roam abroad. However, on attaining his fiftieth birthday +he decided to see something of his country, and especially to pay a +visit to a very old friend living at the town marked Z. <span class='pagenum'>Pg 73<a name="Page_73" id="Page_73"></a></span>What he +proposed was this: that he would start from his home, enter every town +once and only once, and finish his journey at Z. As he made up his +mind to perform this grand tour by rail only, he found it rather a +puzzle to work out his route, but he at length succeeded in doing so. +How did he manage it? Do not forget that every town has to be visited +once, and not more than once.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q250.png" width="400" height="345" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_251_WATER_GAS_AND_ELECTRICITY" id="X_251_WATER_GAS_AND_ELECTRICITY"></a><a href="#X_251_WATER_GAS_AND_ELECTRICITYa"><b>251.—WATER, GAS, AND ELECTRICITY.</b></a></p> + +<p>There are some half-dozen puzzles, as old as the hills, that are +perpetually cropping up, and there is hardly a month in the year that +does not bring inquiries as to their solution. Occasionally one of +these, that one had thought was an extinct volcano, bursts into +eruption in a surprising manner. I have received an extraordinary +number of letters respecting the ancient puzzle that I have called +"Water, Gas, and Electricity." It is much older than electric +lighting, or even gas, but the new dress brings it up to date. The +puzzle is to lay on water, gas, and electricity, from W, G, and E, to +each of the three houses, A, B, and C, without any pipe crossing +another. Take your pencil and draw lines showing how this should be +done. You will soon find yourself landed in difficulties.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q251.png" width="400" height="233" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_252_A_PUZZLE_FOR_MOTORISTS" id="X_252_A_PUZZLE_FOR_MOTORISTS"></a><a href="#X_252_A_PUZZLE_FOR_MOTORISTSa"><b>252.—A PUZZLE FOR MOTORISTS.</b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q252.png" width="600" height="343" alt="" title="" /> +</div> + +<p>Eight motorists drove to church one morning. Their respective houses +and churches, together with the only roads available (the dotted +lines), are shown. One went from his house A to his church A, another +from his house B to his church B, another from C to C, and so on, but +it was afterwards found that no driver ever crossed the track of +another car. Take your pencil and try to trace out their various +routes.</p> + +<hr style="width: 30%;" /> +<p><a name="X_253_A_BANK_HOLIDAY_PUZZLE" id="X_253_A_BANK_HOLIDAY_PUZZLE"></a><a href="#X_253_A_BANK_HOLIDAY_PUZZLEa"><b>253.—A BANK HOLIDAY PUZZLE.</b></a></p> + +<p>Two friends were spending their bank holiday on a cycling trip. +Stopping for a rest at a village inn, they consulted a route map, +which is represented in our illustration in an exceedingly simplified +form, for the puzzle is interesting enough without all the original +complexities. They started from the town in the top left-hand corner +marked A. It will be seen that there are one hundred and twenty such +towns, all connected by straight roads. Now they discovered that there +are exactly 1,365 different routes by which they may reach their +destina<span class='pagenum'>Pg 74<a name="Page_74" id="Page_74"></a></span>tion, always travelling either due south or due east. The +puzzle is to discover which town is their destination.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q253.png" width="400" height="343" alt="" title="" /> +</div> + +<p>Of course, if you find that there are more than 1,365 different routes +to a town it cannot be the right one.</p> + +<hr style="width: 30%;" /> +<p><a name="X_254_THE_MOTOR-CAR_TOUR" id="X_254_THE_MOTOR-CAR_TOUR"></a><a href="#X_254_THE_MOTOR-CAR_TOURa"><b>254.—THE MOTOR-CAR TOUR.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q254.png" width="400" height="377" alt="" title="" /> +</div> + +<p>In the above diagram the circles represent towns and the lines good +roads. In just how many different ways can a motorist, starting from +London (marked with an L), make a tour of all these towns, visiting +every town once, and only once, on a tour, and always coming back to +London on the last ride? The exact reverse of any route is not +counted as different.</p> + +<hr style="width: 30%;" /> +<p><a name="X_255_THE_LEVEL_PUZZLE" id="X_255_THE_LEVEL_PUZZLE"></a><a href="#X_255_THE_LEVEL_PUZZLEa"><b>255.—THE LEVEL PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q255.png" width="400" height="396" alt="" title="" /> +</div> + +<p>This is a simple counting puzzle. In how many different ways can you +spell out the word LEVEL by placing the point of your pencil on an L +and then passing along the lines from letter to letter. You may go in +any direction, backwards or forwards. Of course you are not allowed to +miss letters—that is to say, if you come to a letter you must use it.</p> + +<hr style="width: 30%;" /> +<p><a name="X_256_THE_DIAMOND_PUZZLE" id="X_256_THE_DIAMOND_PUZZLE"></a><a href="#X_256_THE_DIAMOND_PUZZLEa"><b>256.—THE DIAMOND PUZZLE.</b></a></p> + +<p>IN how many different ways may the word DIAMOND be read in the +arrangement shown? You may start wherever you like at a D and go up or +down, backwards or forwards, in and out, in any direction you like, so +long as you always pass from one letter to another that adjoins it. +How many ways are there?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q256.png" width="400" height="405" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_257_THE_DEIFIED_PUZZLE" id="X_257_THE_DEIFIED_PUZZLE"></a><a href="#X_257_THE_DEIFIED_PUZZLEa"><b>257.—THE DEIFIED PUZZLE.</b></a></p> + +<p>In how many different ways may the word DEIFIED be read in this +arrangement under <span class='pagenum'>Pg 75<a name="Page_75" id="Page_75"></a></span>the same conditions as in the last puzzle, with the +addition that you can use any letters twice in the same reading?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q257.png" width="400" height="400" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_258_THE_VOTERS_PUZZLE" id="X_258_THE_VOTERS_PUZZLE"></a><a href="#X_258_THE_VOTERS_PUZZLEa"><b>258.—THE VOTERS' PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q258.png" width="400" height="393" alt="" title="" /> +</div> + +<p>Here we have, perhaps, the most interesting form of the puzzle. In how +many different ways can you read the political injunction, "RISE TO +VOTE, SIR," under the same conditions as before? In this case every +reading of the palindrome requires the use of the central V as the +middle letter.</p> + +<hr style="width: 30%;" /> +<p><a name="X_259_HANNAHS_PUZZLE" id="X_259_HANNAHS_PUZZLE"></a><a href="#X_259_HANNAHS_PUZZLEa"><b>259.—HANNAH'S PUZZLE.</b></a></p> + +<p>A man was in love with a young lady whose Christian name was Hannah. +When he asked her to be his wife she wrote down the letters of her +name in this manner:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q259.png" width="400" height="210" alt="" title="" /> +</div> + +<p>and promised that she would be his if he could tell her correctly in +how many different ways it was possible to spell out her name, always +passing from one letter to another that was adjacent. Diagonal steps +are here allowed. Whether she did this merely to tease him or to test +his cleverness is not recorded, but it is satisfactory to know that he +succeeded. Would you have been equally successful? Take your pencil +and try. You may start from any of the H's and go backwards or +forwards and in any direction, so long as all the letters in a +spelling are adjoining one another. How many ways are there, no two +exactly alike?</p> + +<hr style="width: 30%;" /> +<p><a name="X_260_THE_HONEYCOMB_PUZZLE" id="X_260_THE_HONEYCOMB_PUZZLE"></a><a href="#X_260_THE_HONEYCOMB_PUZZLEa"><b>260.—THE HONEYCOMB PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q260.png" width="400" height="353" alt="" title="" /> +</div> + +<p>Here is a little puzzle with the simplest possible conditions. Place +the point of your pencil on a letter in one of the cells of the +honeycomb, and trace out a very familiar proverb by passing always +from a cell to one that is contiguous to it. If you take the right +route you will have visited every cell once, and only once. The puzzle +is much easier than it looks.</p> + +<hr style="width: 30%;" /> +<p><a name="X_261_THE_MONK_AND_THE_BRIDGES" id="X_261_THE_MONK_AND_THE_BRIDGES"></a><a href="#X_261_THE_MONK_AND_THE_BRIDGESa"><b>261.—THE MONK AND THE BRIDGES.</b></a></p> + +<p>In this case I give a rough plan of a river with an island and five +bridges. On one side of the river is a monastery, and on the other +side is seen a monk in the foreground. Now, the monk has decided that +he will cross every bridge once, and only once, on his return to the +monastery. This is, of course, quite easy to do, but on the way he +thought to himself, "I wonder how many different routes there are from +which I might have selected." Could you have told him? That is the +puzzle. Take your pencil and trace out a route that will take you once +<span class='pagenum'>Pg 76<a name="Page_76" id="Page_76"></a></span>over all the five bridges. Then trace out a second route, then a +third, and see if you can count all the variations. You will find that +the difficulty is twofold: you have to avoid dropping routes on the +one hand and counting the same routes more than once on the other.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q261.png" width="600" height="400" alt="" title="" /> +</div> + + + +<hr style="width: 65%;" /> +<h2><a name="COMBINATION_AND_GROUP_PROBLEMS" id="COMBINATION_AND_GROUP_PROBLEMS"></a><a href="#CONTENTS">COMBINATION AND GROUP PROBLEMS.</a></h2> + +<p class='center'> +"A combination and a form indeed."<br /> +<span style="margin-left: 8em;"><i>Hamlet</i>, iii. 4.</span><br /> +</p> + +<p>Various puzzles in this class might be termed problems in the +"geometry of situation," but their solution really depends on the +theory of combinations which, in its turn, is derived directly from +the theory of permutations. It has seemed convenient to include here +certain group puzzles and enumerations that might, perhaps, with equal +reason have been placed elsewhere; but readers are again asked not to +be too critical about the classification, which is very difficult and +arbitrary. As I have included my problem of "The Round Table" (No. +273), perhaps a few remarks on another well-known problem of the same +class, known by the French as La Problême des Ménages, may be +interesting. If <i>n</i> married ladies are seated at a round table in any +determined order, in how many different ways may their <i>n</i> husbands be +placed so that every man is between two ladies but never next to his +own wife?</p> + +<p>This difficult problem was first solved by Laisant, and the method +shown in the following table is due to Moreau:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="2" summary=""> +<tr><td align='right'>4</td><td align='right'>0</td><td align='right'>2</td></tr> +<tr><td align='right'>5</td><td align='right'>3</td><td align='right'>13</td></tr> +<tr><td align='right'>6</td><td align='right'>13</td><td align='right'>80</td></tr> +<tr><td align='right'>7</td><td align='right'>83</td><td align='right'>579</td></tr> +<tr><td align='right'>8</td><td align='right'>592</td><td align='right'>4738</td></tr> +<tr><td align='right'>9</td><td align='right'>4821</td><td align='right'>43387</td></tr> +<tr><td align='right'>10</td><td align='right'>43979</td><td align='right'>439792</td></tr> +</table></div> + +<p>The first column shows the number of married couples. The numbers in +the second column are obtained in this way: 5 × 3 + 0 - 2 = 13; 6 × 13 + +3 + 2 = 83; 7 × 83 + 13 - 2 = 592; 8 × 592 + 83 + 2 = 4821; and so on. +Find all the numbers, except 2, in the table, and the method will be +evident. It will be noted that the 2 is subtracted when the first +number (the number of couples) is odd, and added when that number is +even. The numbers in the third column are obtained thus: 13 - 0 = 13; 83 +- 3 = 80; 592 - 13 = 579; 4821 - 83 = 4738; and so on. The numbers in +this last column give the required solutions. Thus, four husbands may +be seated in two ways, five husbands may be placed in thirteen ways, +and six husbands in eighty ways.</p> + +<p>The following method, by Lucas, will show the remarkable way in which +chessboard analysis may be applied to the solution of a circular +problem of this kind. Divide a square into thirty-six cells, six by +six, and strike out all the cells in the long diagonal from the bottom +left-hand corner to the top right-hand corner, also the five cells in +the diagonal next above it and the cell in the bottom right-hand +corner. The answer for six couples will be the same as the number of +ways in which you can place six rooks (not using the cancelled cells) +so that no rook shall ever attack another rook. It will be found that +the six rooks may be placed in eighty different ways, which agrees +with the above table.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 77<a name="Page_77" id="Page_77"></a></span><a name="X_262_THOSE_FIFTEEN_SHEEP" id="X_262_THOSE_FIFTEEN_SHEEP"></a><a href="#X_262_THOSE_FIFTEEN_SHEEPa"><b>262.—THOSE FIFTEEN SHEEP.</b></a></p> + +<p>A certain cyclopædia has the following curious problem, I am told: +"Place fifteen sheep in four pens so that there shall be the same +number of sheep in each pen." No answer whatever is vouchsafed, so I +thought I would investigate the matter. I saw that in dealing with +apples or bricks the thing would appear to be quite impossible, since +four times any number must be an even number, while fifteen is an odd +number. I thought, therefore, that there must be some quality peculiar +to the sheep that was not generally known. So I decided to interview +some farmers on the subject. The first one pointed out that if we put +one pen inside another, like the rings of a target, and placed all +sheep in the smallest pen, it would be all right. But I objected to +this, because you admittedly place all the sheep in one pen, not in +four pens. The second man said that if I placed four sheep in each of +three pens and three sheep in the last pen (that is fifteen sheep in +all), and one of the ewes in the last pen had a lamb during the night, +there would be the same number in each pen in the morning. This also +failed to satisfy me.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q262.png" width="600" height="384" alt="" title="" /> +</div> + +<p>The third farmer said, "I've got four hurdle pens down in one of my +fields, and a small flock of wethers, so if you will just step down +with me I will show you how it is done." The illustration depicts my +friend as he is about to demonstrate the matter to me. His lucid +explanation was evidently that which was in the mind of the writer of +the article in the cyclopædia. What was it? Can you place those +fifteen sheep?</p> + +<hr style="width: 30%;" /> +<p><a name="X_263_KING_ARTHURS_KNIGHTS" id="X_263_KING_ARTHURS_KNIGHTS"></a><a href="#X_263_KING_ARTHURS_KNIGHTSa"><b>263.—KING ARTHUR'S KNIGHTS.</b></a></p> + +<p>King Arthur sat at the Round Table on three successive evenings with +his knights—Beleobus, Caradoc, Driam, Eric, Floll, and Galahad—but +on no occasion did any person have as his neighbour one who had before +sat next to him. On the first evening they sat in alphabetical order +round the table. But afterwards King Arthur arranged the two next +sittings so that he might have Beleobus as near to him as possible and +Galahad as far away from him as could be managed. How did he seat the +knights to the best advantage, remembering that rule that no knight +may have the same neighbour twice?</p> + +<hr style="width: 30%;" /> +<p><a name="X_264_THE_CITY_LUNCHEONS" id="X_264_THE_CITY_LUNCHEONS"></a><a href="#X_264_THE_CITY_LUNCHEONSa"><b>264.—THE CITY LUNCHEONS.</b></a></p> + +<p>Twelve men connected with a large firm in the City of London sit down +to luncheon together every day in the same room. The tables are small +ones that only accommodate two persons at the same time. Can you show +how these twelve men may lunch together on eleven days in pairs, so +that no two of them shall ever sit twice together? We will represent +the men by the first twelve letters of the alphabet, and suppose the +first day's pairing to be as follows—</p> + +<p> +<span style="margin-left: 2em;">(A B) (C D) (E F) (G H) (I J) (K L).</span><br /> +</p> + +<p>Then give any pairing you like for the next day, say—</p> + +<p> +<span style="margin-left: 2em;">(A C) (B D) (E G) (F H) (I K) (J L),</span><br /> +</p> + +<p>and so on, until you have completed your eleven lines, with no pair +ever occurring twice. There are a good many different arrangements +possible. Try to find one of them.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 78<a name="Page_78" id="Page_78"></a></span><a name="X_265_A_PUZZLE_FOR_CARD-PLAYERS" id="X_265_A_PUZZLE_FOR_CARD-PLAYERS"></a><a href="#X_265_A_PUZZLE_FOR_CARD-PLAYERSa"><b>265.—A PUZZLE FOR CARD-PLAYERS.</b></a></p> + +<p>Twelve members of a club arranged to play bridge together on eleven +evenings, but no player was ever to have the same partner more than +once, or the same opponent more than twice. Can you draw up a scheme +showing how they may all sit down at three tables every evening? Call +the twelve players by the first twelve letters of the alphabet and try +to group them.</p> + +<hr style="width: 30%;" /> +<p><a name="X_266_A_TENNIS_TOURNAMENT" id="X_266_A_TENNIS_TOURNAMENT"></a><a href="#X_266_A_TENNIS_TOURNAMENTa"><b>266.—A TENNIS TOURNAMENT.</b></a></p> + +<p>Four married couples played a "mixed double" tennis tournament, a man +and a lady always playing against a man and a lady. But no person ever +played with or against any other person more than once. Can you show +how they all could have played together in the two courts on three +successive days? This is a little puzzle of a quite practical kind, +and it is just perplexing enough to be interesting.</p> + +<hr style="width: 30%;" /> +<p><a name="X_267_THE_WRONG_HATS" id="X_267_THE_WRONG_HATS"></a><a href="#X_267_THE_WRONG_HATSa"><b>267.—THE WRONG HATS.</b></a></p> + +<p>"One of the most perplexing things I have come across lately," said +Mr. Wilson, "is this. Eight men had been dining not wisely but too +well at a certain London restaurant. They were the last to leave, but +not one man was in a condition to identify his own hat. Now, +considering that they took their hats at random, what are the chances +that every man took a hat that did not belong to him?"</p> + +<p>"The first thing," said Mr. Waterson, "is to see in how many different +ways the eight hats could be taken."</p> + +<p>"That is quite easy," Mr. Stubbs explained. "Multiply together the +numbers, 1, 2, 3, 4, 5, 6, 7, and 8. Let me see—half a minute—yes; +there are 40,320 different ways."</p> + +<p>"Now all you've got to do is to see in how many of these cases no man +has his own hat," said Mr. Waterson.</p> + +<p>"Thank you, I'm not taking any," said Mr. Packhurst. "I don't envy the +man who attempts the task of writing out all those forty-thousand-odd +cases and then picking out the ones he wants."</p> + +<p>They all agreed that life is not long enough for that sort of +amusement; and as nobody saw any other way of getting at the answer, +the matter was postponed indefinitely. Can you solve the puzzle?</p> + +<hr style="width: 30%;" /> +<p><a name="X_268_THE_PEAL_OF_BELLS" id="X_268_THE_PEAL_OF_BELLS"></a><a href="#X_268_THE_PEAL_OF_BELLSa"><b>268.—THE PEAL OF BELLS.</b></a></p> + +<p>A correspondent, who is apparently much interested in campanology, +asks me how he is to construct what he calls a "true and correct" peal +for four bells. He says that every possible permutation of the four +bells must be rung once, and once only. He adds that no bell must move +more than one place at a time, that no bell must make more than two +successive strokes in either the first or the last place, and that the +last change must be able to pass into the first. These fantastic +conditions will be found to be observed in the little peal for three +bells, as follows:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>1</td><td align='right'>2</td><td align='right'>3</td></tr> +<tr><td align='right'>2</td><td align='right'>1</td><td align='right'>3</td></tr> +<tr><td align='right'>2</td><td align='right'>3</td><td align='right'>1</td></tr> +<tr><td align='right'>3</td><td align='right'>2</td><td align='right'>1</td></tr> +<tr><td align='right'>3</td><td align='right'>1</td><td align='right'>2</td></tr> +<tr><td align='right'>1</td><td align='right'>3</td><td align='right'>2</td></tr> +</table></div> + + +<p>How are we to give him a correct solution for his four bells?</p> + +<hr style="width: 30%;" /> +<p><a name="X_269_THREE_MEN_IN_A_BOAT" id="X_269_THREE_MEN_IN_A_BOAT"></a><a href="#X_269_THREE_MEN_IN_A_BOATa"><b>269.—THREE MEN IN A BOAT.</b></a></p> + +<p>A certain generous London manufacturer gives his workmen every year a +week's holiday at the seaside at his own expense. One year fifteen of +his men paid a visit to Herne Bay. On the morning of their departure +from London they were addressed by their employer, who expressed the +hope that they would have a very pleasant time.</p> + +<p>"I have been given to understand," he added, "that some of you fellows +are very fond of rowing, so I propose on this occasion to provide you +with this recreation, and at the same time give you an amusing little +puzzle to solve. During the seven days that you are at Herne Bay every +one of you will go out every day at the same time for a row, but there +must always be three men in a boat and no more. No two men may ever go +out in a boat together more than once, and no man is allowed to go out +twice in the same boat. If you can manage to do this, and use as few +different boats as possible, you may charge the firm with the +expense."</p> + +<p>One of the men tells me that the experience he has gained in such +matters soon enabled him to work out the answer to the entire +satisfaction of themselves and their employer. But the amusing part of +the thing is that they never really solved the little mystery. I find +their method to have been quite incorrect, and I think it will amuse +my readers to discover how the men should have been placed in the +boats. As their names happen to have been Andrews, Baker, Carter, +Danby, Edwards, Frith, Gay, Hart, Isaacs, Jackson, Kent, Lang, Mason, +Napper, and Onslow, we can call them by their initials and write out +the five groups for each of the seven days in the following simple +way:</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'></td><td align='center'>1</td><td align='center'>2</td><td align='center'>3</td><td align='center'>4</td><td align='center'>5</td></tr> +<tr><td align='center'>First Day:</td><td align='center'>(ABC)</td><td align='center'>(DEF)</td><td align='center'>(GHI)</td><td align='center'>(JKL)</td><td align='center'>(MNO).</td></tr> +</table></div> + +<p>The men within each pair of brackets are here seen to be in the same +boat, and therefore A can never go out with B or with C again, and C +can never go out again with B. The same applies to the other four +boats. The figures show the number on the boat, so that A, B, or C, +for example, can never go out in boat No. 1 again.</p> + +<hr style="width: 30%;" /> +<p><a name="X_270_THE_GLASS_BALLS" id="X_270_THE_GLASS_BALLS"></a><a href="#X_270_THE_GLASS_BALLSa"><b>270.—THE GLASS BALLS.</b></a></p> + +<p>A number of clever marksmen were staying at a country house, and the +host, to provide a little amusement, suspended strings of glass balls, +as shown in the illustration, to be fired <span class='pagenum'>Pg 79<a name="Page_79" id="Page_79"></a></span>at. After they had all put +their skill to a sufficient test, somebody asked the following +question: "What is the total number of different ways in which these +sixteen balls may be broken, if we must always break the lowest ball +that remains on any string?" Thus, one way would be to break all the +four balls on each string in succession, taking the strings from left +to right. Another would be to break all the fourth balls on the four +strings first, then break the three remaining on the first string, +then take the balls on the three other strings alternately from right +to left, and so on. There is such a vast number of different ways +(since every little variation of order makes a different way) that one +is apt to be at first impressed by the great difficulty of the +problem. Yet it is really quite simple when once you have hit on the +proper method of attacking it. How many different ways are there?</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q270.png" width="600" height="488" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_271_FIFTEEN_LETTER_PUZZLE" id="X_271_FIFTEEN_LETTER_PUZZLE"></a><a href="#X_271_FIFTEEN_LETTER_PUZZLEa"><b>271.—FIFTEEN LETTER PUZZLE.</b></a></p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>ALE</td><td align='center'>FOE</td><td align='center'>HOD</td><td align='center'>BGN</td></tr> +<tr><td align='center'>CAB</td><td align='center'>HEN</td><td align='center'>JOG</td><td align='center'>KFM</td></tr> +<tr><td align='center'>HAG</td><td align='center'>GEM</td><td align='center'>MOB</td><td align='center'>BFH</td></tr> +<tr><td align='center'>FAN</td><td align='center'>KIN</td><td align='center'>JEK</td><td align='center'>DFL</td></tr> +<tr><td align='center'>JAM</td><td align='center'>HIM</td><td align='center'>GCL</td><td align='center'>LJH</td></tr> +<tr><td align='center'>AID</td><td align='center'>JIB</td><td align='center'>FCJ</td><td align='center'>NJD</td></tr> +<tr><td align='center'>OAK</td><td align='center'>FIG</td><td align='center'>HCK</td><td align='center'>MLN</td></tr> +<tr><td align='center'>BED</td><td align='center'>OIL</td><td align='center'>MCD</td><td align='center'>BLK</td></tr> +<tr><td align='center'>ICE</td><td align='center'>CON</td><td align='center'>DGK</td></tr> +</table></div> + +<p>The above is the solution of a puzzle I gave in <i>Tit-bits</i> in the +summer of 1896. It was required to take the letters, A, B, C, D, E, F, +G, H, I, J, K, L, M, N, and O, and with them form thirty-five groups +of three letters so that the combinations should include the greatest +number possible of common English words. No two letters may appear +together in a group more than once. Thus, A and L having been together +in ALE, must never be found together again; nor may A appear again in +a group with E, nor L with E. These conditions will be found complied +with in the above solution, and the number of words formed is +twenty-one. Many persons have since tried hard to beat this number, +but so far have not succeeded.</p> + +<p>More than thirty-five combinations of the fifteen letters cannot be +formed within the conditions. Theoretically, there cannot possibly be +more than twenty-three words formed, because only this number of +combinations is possible with a vowel or vowels in each. And as no +English word can be formed from three of the given vowels (A, E, I, +and O), we must reduce the number of possible words to twenty-two. +This is correct theoretically, but practically that twenty-second word +cannot be got in. If JEK, shown above, were a word it would be all +right; but it is not, and no amount of juggling with the other letters +has resulted in a better answer than the one shown. I should, say that +proper nouns and abbreviations, such as Joe, Jim, Alf, Hal, Flo, Ike, +etc., are disallowed.</p> + +<p>Now, the present puzzle is a variation of the above. It is simply +this: Instead of using the fifteen letters given, the reader is +allowed to select any fifteen different letters of the alphabet that +he may prefer. Then construct thirty-five <span class='pagenum'>Pg 80<a name="Page_80" id="Page_80"></a></span>groups in accordance with +the conditions, and show as many good English words as possible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_272_THE_NINE_SCHOOLBOYS" id="X_272_THE_NINE_SCHOOLBOYS"></a><a href="#X_272_THE_NINE_SCHOOLBOYSa"><b>272.—THE NINE SCHOOLBOYS.</b></a></p> + +<p>This is a new and interesting companion puzzle to the "Fifteen +Schoolgirls" (see solution of No. 269), and even in the simplest +possible form in which I present it there are unquestionable +difficulties. Nine schoolboys walk out in triplets on the six week +days so that no boy ever walks <i>side by side</i> with any other boy more +than once. How would you arrange them?</p> + +<p>If we represent them by the first nine letters of the alphabet, they +might be grouped on the first day as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>A</td><td align='center'>B</td><td align='center'>C</td></tr> +<tr><td align='center'>D</td><td align='center'>E</td><td align='center'>F</td></tr> +<tr><td align='center'>G</td><td align='center'>H</td><td align='center'>I</td></tr> +</table></div> + +<p>Then A can never walk again side by side with B, or B with C, or D +with E, and so on. But A can, of course, walk side by side with C. It +is here not a question of being together in the same triplet, but of +walking side by side in a triplet. Under these conditions they can +walk out on six days; under the "Schoolgirls" conditions they can only +walk on four days.</p> + +<hr style="width: 30%;" /> +<p><a name="X_273_THE_ROUND_TABLE" id="X_273_THE_ROUND_TABLE"></a><a href="#X_273_THE_ROUND_TABLEa"><b>273.—THE ROUND TABLE.</b></a></p> + +<p>Seat the same <i>n</i> persons at a round table on</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' class='bb'>(n - 1)(n - 2)</td></tr> +<tr><td align='center'>2</td></tr> +</table></div> + +<p>occasions so that no person shall ever have the same two neighbours +twice. This is, of course, equivalent to saying that every person must +sit once, and once only, between every possible pair.</p> + +<hr style="width: 30%;" /> +<p><a name="X_274_THE_MOUSE-TRAP_PUZZLE" id="X_274_THE_MOUSE-TRAP_PUZZLE"></a><a href="#X_274_THE_MOUSE-TRAP_PUZZLEa"><b>274.—THE MOUSE-TRAP PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q274.png" width="400" height="397" alt="" title="" /> +</div> + +<p>This is a modern version, with a difference, of an old puzzle of the +same name. Number twenty-one cards, 1, 2, 3, etc., up to 21, and place +them in a circle in the particular order shown in the illustration. +These cards represent mice. You start from any card, calling that card +"one," and count, "one, two, three," etc., in a clockwise direction, +and when your count agrees with the number on the card, you have made +a "catch," and you remove the card. Then start at the next card, +calling that "one," and try again to make another "catch." And so on. +Supposing you start at 18, calling that card "one," your first "catch" +will be 19. Remove 19 and your next "catch" is 10. Remove 10 and your +next "catch" is 1. Remove the 1, and if you count up to 21 (you must +never go beyond), you cannot make another "catch." Now, the ideal is +to "catch" all the twenty-one mice, but this is not here possible, and +if it were it would merely require twenty-one different trials, at the +most, to succeed. But the reader may make any two cards change places +before he begins. Thus, you can change the 6 with the 2, or the 7 with +the 11, or any other pair. This can be done in several ways so as to +enable you to "catch" all the twenty-one mice, if you then start at +the right place. You may never pass over a "catch"; you must always +remove the card and start afresh.</p> + +<hr style="width: 30%;" /> +<p><a name="X_275_THE_SIXTEEN_SHEEP" id="X_275_THE_SIXTEEN_SHEEP"></a><a href="#X_275_THE_SIXTEEN_SHEEPa"><b>275.—THE SIXTEEN SHEEP.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q275.png" width="400" height="402" alt="" title="" /> +</div> + +<p>Here is a new puzzle with matches and counters or coins. In the +illustration the matches represent hurdles and the counters sheep. The +sixteen hurdles on the outside, and the sheep, must be regarded as +immovable; the puzzle has to do entirely with the nine hurdles on the +inside. It will be seen that at present these nine hurdles enclose +four groups of 8, 3, 3, and 2 sheep. The farmer requires to readjust +some of the hurdles so as to enclose 6, 6, and 4 sheep. Can you do it +by only replacing two hurdles? When you have succeeded, then try to +do it by replacing three hurdles; then four, five, six, and seven in +succession. Of course, the hurdles must be legitimately laid on the +dotted lines, and no such tricks are allowed as leaving unconnected +ends of hurdles, or two hurdles placed side by side, or merely making +hurdles change places. In fact, the conditions are so simple that any +farm labourer will understand it directly.</p> + +<hr style="width: 30%;" /> +<p><a name="X_276_THE_EIGHT_VILLAS" id="X_276_THE_EIGHT_VILLAS"></a><a href="#X_276_THE_EIGHT_VILLASa"><b>276.—THE EIGHT VILLAS.</b></a></p> + +<p>In one of the outlying suburbs of London a man had a square plot of +ground on which he <span class='pagenum'>Pg 81<a name="Page_81" id="Page_81"></a></span>decided to build eight villas, as shown in the +illustration, with a common recreation ground in the middle. After the +houses were completed, and all or some of them let, he discovered that +the number of occupants in the three houses forming a side of the +square was in every case nine. He did not state how the occupants were +distributed, but I have shown by the numbers on the sides of the +houses one way in which it might have happened. The puzzle is to +discover the total number of ways in which all or any of the houses +might be occupied, so that there should be nine persons on each side. +In order that there may be no misunderstanding, I will explain that +although B is what we call a reflection of A, these would count as two +different arrangements, while C, if it is turned round, will give four +arrangements; and if turned round in front of a mirror, four other +arrangements. All eight must be counted.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q276.png" width="400" height="533" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_277_COUNTER_CROSSES" id="X_277_COUNTER_CROSSES"></a><a href="#X_277_COUNTER_CROSSESa"><b>277.—COUNTER CROSSES.</b></a></p> + +<p>All that we need for this puzzle is nine counters, numbered 1, 2, 3, +4, 5, 6, 7, 8, and 9. It will be seen that in the illustration A these +are arranged so as to form a Greek cross, while in the case of B they +form a Latin cross. In both cases the reader will find that the sum of +the numbers in the upright of the cross is the same as the sum of the +numbers in the horizontal arm. It is quite easy to hit on such an +arrangement by trial, but the problem is to discover in exactly how +many different ways it may be done in each case. Remember that +reversals and reflections do not count as different. That is to say, +if you turn this page round you get four arrangements of the Greek +cross, and if you turn it round again in front of a mirror you will +get four more. But these eight are all regarded as one and the same. +Now, how many different ways are there in each case?</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q277.png" width="600" height="295" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_278_A_DORMITORY_PUZZLE" id="X_278_A_DORMITORY_PUZZLE"></a><a href="#X_278_A_DORMITORY_PUZZLEa"><b>278.—A DORMITORY PUZZLE.</b></a></p> + +<p>In a certain convent there were eight large dormitories on one floor, +approached by a spiral staircase in the centre, as shown in our plan. +On an inspection one Monday by the abbess it was found that the south +aspect was so much preferred that six times as many nuns slept on the +south side as on each of the other three sides. She objected to this +overcrowding, and ordered that it should be reduced. On Tuesday she +found that five times as many slept on the south side as on each of +the other sides. Again she complained. On Wednesday she found four +times as many on the south side, on Thursday three times as many, and +on Friday twice as many. Urging the nuns to further efforts, she was +pleased to find on Saturday that an equal number slept on each of the +four <span class='pagenum'>Pg 82<a name="Page_82" id="Page_82"></a></span>sides of the house. What is the smallest number of nuns there +could have been, and how might they have arranged themselves on each +of the six nights? No room may ever be unoccupied.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q278.png" width="400" height="393" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_279_THE_BARRELS_OF_BALSAM" id="X_279_THE_BARRELS_OF_BALSAM"></a><a href="#X_279_THE_BARRELS_OF_BALSAMa"><b>279.—THE BARRELS OF BALSAM.</b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q279.png" width="600" height="446" alt="" title="" /> +</div> + +<p>A merchant of Bagdad had ten barrels of precious balsam for sale. +They were numbered, and were arranged in two rows, one on top of the +other, as shown in the picture. The smaller the number on the barrel, +the greater was its value. So that the best quality was numbered "1" and +the worst numbered "10," and all the other numbers of graduating values. +Now, the rule of Ahmed Assan, the merchant, was that he never put a +barrel either beneath or to the right of one of less value. The +arrangement shown is, of course, the simplest way of complying with this +condition. But there are many other ways—such, for example, as +this:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>1</td><td align='right'>2</td><td align='right'>5</td><td align='right'>7</td><td align='right'>8</td></tr> +<tr><td align='right'>3</td><td align='right'>4</td><td align='right'>6</td><td align='right'>9</td><td align='right'>10</td></tr> +</table></div> + +<p>Here, again, no barrel has a smaller number than itself on its right +or beneath it. The puzzle is to discover in how many different ways +the merchant of Bagdad might have arranged his barrels in the two rows +without breaking his rule. Can you count the number of ways?</p> + +<hr style="width: 30%;" /> +<p><a name="X_280_BUILDING_THE_TETRAHEDRON" id="X_280_BUILDING_THE_TETRAHEDRON"></a><a href="#X_280_BUILDING_THE_TETRAHEDRONa"><b>280.—BUILDING THE TETRAHEDRON.</b></a></p> + +<p>I possess a tetrahedron, or triangular pyramid, formed of six sticks +glued together, as shown in the illustration. Can you count correctly +the number of different ways in which these six sticks might have been +stuck together so as to form the pyramid?</p> + +<p>Some friends worked at it together one evening, each person providing +himself with six lucifer matches to aid his thoughts; but it was found +that no two results were the same. You see, if we remove one of the +sticks and turn it round the other way, that will be a different +pyramid. If we make two of the sticks change <span class='pagenum'>Pg 83<a name="Page_83" id="Page_83"></a></span>places the result will +again be different. But remember that every pyramid may be made to +stand on either of its four sides without being a different one. How +many ways are there altogether?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q280.png" width="400" height="347" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_281_PAINTING_A_PYRAMID" id="X_281_PAINTING_A_PYRAMID"></a><a href="#X_281_PAINTING_A_PYRAMIDa"><b>281.—PAINTING A PYRAMID.</b></a></p> + +<p>This puzzle concerns the painting of the four sides of a tetrahedron, +or triangular pyramid. If you cut out a piece of cardboard of the +triangular shape shown in Fig. 1, and then cut half through along the +dotted lines, it will fold up and form a perfect triangular pyramid. +And I would first remind my readers that the primary colours of the +solar spectrum are seven—violet, indigo, blue, green, yellow, orange, +and red. When I was a child I was taught to remember these by the +ungainly word formed by the initials of the colours, "Vibgyor."</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q281.png" width="600" height="246" alt="" title="" /> +</div> + +<p>In how many different ways may the triangular pyramid be coloured, +using in every case one, two, three, or four colours of the solar +spectrum? Of course a side can only receive a single colour, and no +side can be left uncoloured. But there is one point that I must make +quite clear. The four sides are not to be regarded as individually +distinct. That is to say, if you paint your pyramid as shown in Fig. 2 +(where the bottom side is green and the other side that is out of view +is yellow), and then paint another in the order shown in Fig. 3, these +are really both the same and count as one way. For if you tilt over +No. 2 to the right it will so fall as to represent No. 3. The +avoidance of repetitions of this kind is the real puzzle of the thing. +If a coloured pyramid cannot be placed so that it exactly resembles in +its colours and their relative order another pyramid, then they are +different. Remember that one way would be to colour all the four sides +red, another to colour two sides green, and the remaining sides yellow +and blue; and so on.</p> + +<hr style="width: 30%;" /> +<p><a name="X_282_THE_ANTIQUARYS_CHAIN" id="X_282_THE_ANTIQUARYS_CHAIN"></a><a href="#X_282_THE_ANTIQUARYS_CHAINa"><b>282.—THE ANTIQUARY'S CHAIN.</b></a></p> + +<p>An antiquary possessed a number of curious old links, which he took to +a blacksmith, and told him to join together to form one straight piece +of chain, with the sole condition that the two circular links were not +to be together. The following illustration shows the appearance of the +chain and the form of each link. Now, supposing the owner should +separate the links again, and then take them to another smith and +repeat his former instructions exactly, what are the chances against +the links being put together exactly as they were by the first man? +Remember that every successive link can be joined on to another in one +of two ways, just as you can put a ring on your finger in two ways, or +link your forefingers and thumbs in two ways.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q282.png" width="400" height="191" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_283_THE_FIFTEEN_DOMINOES" id="X_283_THE_FIFTEEN_DOMINOES"></a><a href="#X_283_THE_FIFTEEN_DOMINOESa"><b>283.—THE FIFTEEN DOMINOES.</b></a></p> + +<p>In this case we do not use the complete set of twenty-eight dominoes +to be found in the ordinary box. We dispense with all those dominoes +<span class='pagenum'>Pg 84<a name="Page_84" id="Page_84"></a></span>that have a five or a six on them and limit ourselves to the fifteen +that remain, where the double-four is the highest.</p> + +<p>In how many different ways may the fifteen dominoes be arranged in a +straight line in accordance with the simple rule of the game that a +number must always be placed against a similar number—that is, a four +against a four, a blank against a blank, and so on? Left to right and +right to left of the same arrangement are to be counted as two +different ways.</p> + +<hr style="width: 30%;" /> +<p><a name="X_284_THE_CROSS_TARGET" id="X_284_THE_CROSS_TARGET"></a><a href="#X_284_THE_CROSS_TARGETa"><b>284.—THE CROSS TARGET.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q284.png" width="400" height="314" alt="" title="" /> +</div> + +<p>In the illustration we have a somewhat curious target designed by an +eccentric sharpshooter. His idea was that in order to score you must +hit four circles in as many shots so that those four shots shall form +a square. It will be seen by the results recorded on the target that +two attempts have been successful. The first man hit the four circles +at the top of the cross, and thus formed his square. The second man +intended to hit the four in the bottom arm, but his second shot, on +the left, went too high. This compelled him to complete his four in a +different way than he intended. It will thus be seen that though it is +immaterial which circle you hit at the first shot, the second shot may +commit you to a definite procedure if you are to get your square. Now, +the puzzle is to say in just how many different ways it is possible to +form a square on the target with four shots.</p> + +<hr style="width: 30%;" /> +<p><a name="X_285_THE_FOUR_POSTAGE_STAMPS" id="X_285_THE_FOUR_POSTAGE_STAMPS"></a><a href="#X_285_THE_FOUR_POSTAGE_STAMPSa"><b>285.—THE FOUR POSTAGE STAMPS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q285.png" width="400" height="300" alt="" title="" /> +</div> + +<p>"It is as easy as counting," is an expression one sometimes hears. But +mere counting may be puzzling at times. Take the following simple +example. Suppose you have just bought twelve postage stamps, in this +form—three by four—and a friend asks you to oblige him with four +stamps, all joined together—no stamp hanging on by a mere corner. In +how many different ways is it possible for you to tear off those four +stamps? You see, you can give him 1, 2, 3, 4, or 2, 3, 6, 7, or 1, 2, +3, 6, or 1, 2, 3, 7, or 2, 3, 4, 8, and so on. Can you count the +number of different ways in which those four stamps might be +delivered? There are not many more than fifty ways, so it is not a big +count. Can you get the exact number?</p> + +<hr style="width: 30%;" /> +<p><a name="X_286_PAINTING_THE_DIE" id="X_286_PAINTING_THE_DIE"></a><a href="#X_286_PAINTING_THE_DIEa"><b>286.—PAINTING THE DIE.</b></a></p> + +<p>In how many different ways may the numbers on a single die be marked, +with the only condition that the 1 and 6, the 2 and 5, and the 3 and 4 +must be on opposite sides? It is a simple enough question, and yet it +will puzzle a good many people.</p> + +<hr style="width: 30%;" /> +<p><a name="X_287_AN_ACROSTIC_PUZZLE" id="X_287_AN_ACROSTIC_PUZZLE"></a><a href="#X_287_AN_ACROSTIC_PUZZLEa"><b>287.—AN ACROSTIC PUZZLE.</b></a></p> + +<p>In the making or solving of double acrostics, has it ever occurred to +you to consider the variety and limitation of the pair of initial and +final letters available for cross words? You may have to find a word +beginning with A and ending with B, or A and C, or A and D, and so on. +Some combinations are obviously impossible—such, for example, as +those with Q at the end. But let us assume that a good English word +can be found for every case. Then how many possible pairs of letters +are available?</p> + + + +<hr style="width: 65%;" /> +<h2><a name="CHESSBOARD_PROBLEMS" id="CHESSBOARD_PROBLEMS"></a><a href="#CONTENTS">CHESSBOARD PROBLEMS.</a></h2> + +<p class='center'> +"You and I will goe to the chesse."<br /> +<span style="margin-left: 8em;">GREENE'S <i>Groatsworth of Wit.</i><br /></span> +</p> + +<p>During a heavy gale a chimney-pot was hurled through the air, and +crashed upon the pavement just in front of a pedestrian. He quite +calmly said, "I have no use for it: I do not smoke." Some readers, +when they happen to see a puzzle represented on a chessboard with +chess pieces, are apt to make the equally inconsequent remark, "I have +no use for it: I do not play chess." This is largely a result of the +common, but erroneous, notion that the ordinary chess puzzle with +which we are familiar in the press (dignified, for some reason, with +the name "problem") has a vital connection with the game of chess +itself. But there is no condition in the game that you shall checkmate +your opponent in two moves, in three moves, or in four moves, while +the majority of the positions given in these puzzles are such that one +player would have so great a superiority in pieces that <span class='pagenum'>Pg 85<a name="Page_85" id="Page_85"></a></span>the other +would have resigned before the situations were reached. And the +solving of them helps you but little, and that quite indirectly, in +playing the game, it being well known that, as a rule, the best "chess +problemists" are indifferent players, and <i>vice versa</i>. Occasionally a +man will be found strong on both subjects, but he is the exception to +the rule.</p> + +<p>Yet the simple chequered board and the characteristic moves of the +pieces lend themselves in a very remarkable manner to the devising of +the most entertaining puzzles. There is room for such infinite variety +that the true puzzle lover cannot afford to neglect them. It was with +a view to securing the interest of readers who are frightened off by +the mere presentation of a chessboard that so many puzzles of this +class were originally published by me in various fanciful dresses. +Some of these posers I still retain in their disguised form; others I +have translated into terms of the chessboard. In the majority of cases +the reader will not need any knowledge whatever of chess, but I have +thought it best to assume throughout that he is acquainted with the +terminology, the moves, and the notation of the game.</p> + +<p>I first deal with a few questions affecting the chessboard itself; +then with certain statical puzzles relating to the Rook, the Bishop, +the Queen, and the Knight in turn; then dynamical puzzles with the +pieces in the same order; and, finally, with some miscellaneous +puzzles on the chessboard. It is hoped that the formulæ and tables +given at the end of the statical puzzles will be of interest, as they +are, for the most part, published for the first time.</p> + + + +<h2><a name="THE_CHESSBOARD" id="THE_CHESSBOARD"></a><a href="#CONTENTS">THE CHESSBOARD.</a></h2> + +<p class='center'> +"Good company's a chessboard."<br /> +<span style="margin-left: 8em;">BYRON'S <i>Don Juan</i>, xiii. 89.</span><br /> +</p> + +<p>A chessboard is essentially a square plane divided into sixty-four +smaller squares by straight lines at right angles. Originally it was +not chequered (that is, made with its rows and columns alternately +black and white, or of any other two colours), and this improvement +was introduced merely to help the eye in actual play. The utility of +the chequers is unquestionable. For example, it facilitates the +operation of the bishops, enabling us to see at the merest glance that +our king or pawns on black squares are not open to attack from an +opponent's bishop running on the white diagonals. Yet the chequering +of the board is not essential to the game of chess. Also, when we are +propounding puzzles on the chessboard, it is often well to remember +that additional interest may result from "generalizing" for boards +containing any number of squares, or from limiting ourselves to some +particular chequered arrangement, not necessarily a square. We will +give a few puzzles dealing with chequered boards in this general way.</p> + +<hr style="width: 30%;" /> +<p><a name="X_288_CHEQUERED_BOARD_DIVISIONS" id="X_288_CHEQUERED_BOARD_DIVISIONS"></a><a href="#X_288_CHEQUERED_BOARD_DIVISIONSa"><b>288.—CHEQUERED BOARD DIVISIONS.</b></a></p> + +<p>I recently asked myself the question: In how many different ways may a +chessboard be divided into two parts of the same size and shape by +cuts along the lines dividing the squares? The problem soon proved to +be both fascinating and bristling with difficulties. I present it in a +simplified form, taking a board of smaller dimensions.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q288.png" width="400" height="679" alt="" title="" /> +</div> + +<p>It is obvious that a board of four squares can only be so divided in +one way—by a straight cut down the centre—because we shall not count +reversals and reflections as different. In the case of a board of +sixteen squares—four by four—there are just six different ways. I +have given all these in the diagram, and the reader will not find any +others. Now, take the larger board of thirty-six squares, and try to +discover in how many ways it may be cut into two parts of the same +size and shape.</p> + +<hr style="width: 30%;" /> +<p><a name="X_289_LIONS_AND_CROWNS" id="X_289_LIONS_AND_CROWNS"></a><a href="#X_289_LIONS_AND_CROWNSa"><b>289.—LIONS AND CROWNS.</b></a></p> + +<p>The young lady in the illustration is confronted with a little +cutting-out difficulty in which the reader may be glad to assist her. +She wishes, for some reason that she has not communi<span class='pagenum'>Pg 86<a name="Page_86" id="Page_86"></a></span>cated to me, to +cut that square piece of valuable material into four parts, all of +exactly the same size and shape, but it is important that every piece +shall contain a lion and a crown. As she insists that the cuts can +only be made along the lines dividing the squares, she is considerably +perplexed to find out how it is to be done. Can you show her the way? +There is only one possible method of cutting the stuff.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q289.png" width="400" height="707" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_290_BOARDS_WITH_AN_ODD_NUMBER_OF_SQUARES" id="X_290_BOARDS_WITH_AN_ODD_NUMBER_OF_SQUARES"></a><a href="#X_290_BOARDS_WITH_AN_ODD_NUMBER_OF_SQUARESa"><b>290.—BOARDS WITH AN ODD NUMBER OF SQUARES.</b></a></p> + +<p>We will here consider the question of those boards that contain an odd +number of squares. We will suppose that the central square is first +cut out, so as to leave an even number of squares for division. Now, +it is obvious that a square three by three can only be divided in one +way, as shown in Fig. 1. It will be seen that the pieces A and B are +of the same size and shape, and that any other way of cutting would +only produce the same shaped pieces, so remember that these variations +are not counted as different ways. The puzzle I propose is to cut the +board five by five (Fig. 2) into two pieces of the same size and shape +in as many different ways as possible. I have shown in the +illustration one way of doing it. How many different ways are there +altogether? A piece which when turned over resembles another piece is +not considered to be of a different shape.</p> + +<div class="figcenter" style="width: 130px;"> +<img src="images/q290fig1.png" width="130" height="134" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 250px;"> +<img src="images/q290fig2.png" width="250" height="250" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_291_THE_GRAND_LAMAS_PROBLEM" id="X_291_THE_GRAND_LAMAS_PROBLEM"></a><a href="#X_291_THE_GRAND_LAMAS_PROBLEMa"><b>291.—THE GRAND LAMA'S PROBLEM.</b></a></p> + +<p>Once upon a time there was a Grand Lama who had a chessboard made of +pure gold, magnificently engraved, and, of course, of great value. +Every year a tournament was held at Lhassa among the priests, and +whenever any one beat the Grand Lama it was considered a great honour, +and his name was inscribed on the back of the board, and a costly +jewel set in the particular square on which the checkmate had been +given. After this sovereign pontiff had been defeated on four +occasions he died—possibly of chagrin.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q291.png" width="400" height="394" alt="" title="" /> +</div> + +<p>Now the new Grand Lama was an inferior chess-player, and preferred +other forms of innocent amusement, such as cutting off people's heads. +So he discouraged chess as a degrading game, that did not improve +either the mind or the morals, and abolished the tournament summarily. +Then he sent for the four priests who had had the effrontery to play +better than a Grand Lama, and addressed them as follows: <span class='pagenum'>Pg 87<a name="Page_87" id="Page_87"></a></span>"Miserable +and heathenish men, calling yourselves priests! Know ye not that to +lay claim to a capacity to do anything better than my predecessor is a +capital offence? Take that chessboard and, before day dawns upon the +torture chamber, cut it into four equal parts of the same shape, each +containing sixteen perfect squares, with one of the gems in each part! +If in this you fail, then shall other sports be devised for your +special delectation. Go!" The four priests succeeded in their +apparently hopeless task. Can you show how the board may be divided +into four equal parts, each of exactly the same shape, by cuts along +the lines dividing the squares, each part to contain one of the gems?</p> + +<hr style="width: 30%;" /> +<p><a name="X_292_THE_ABBOTS_WINDOW" id="X_292_THE_ABBOTS_WINDOW"></a><a href="#X_292_THE_ABBOTS_WINDOWa"><b>292.—THE ABBOT'S WINDOW.</b></a></p> + +<p>Once upon a time the Lord Abbot of St. Edmondsbury, in consequence of +"devotions too strong for his head," fell sick and was unable to leave +his bed. As he lay awake, tossing his head restlessly from side to +side, the attentive monks noticed that something was disturbing his +mind; but nobody dared ask what it might be, for the abbot was of a +stern disposition, and never would brook inquisitiveness. Suddenly he +called for Father John, and that venerable monk was soon at the +bedside.</p> + +<p>"Father John," said the Abbot, "dost thou know that I came into this +wicked world on a Christmas Even?"</p> + +<p>The monk nodded assent.</p> + +<p>"And have I not often told thee that, having been born on Christmas +Even, I have no love for the things that are odd? Look there!"</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q292.png" width="400" height="382" alt="" title="" /> +</div> + +<p>The Abbot pointed to the large dormitory window, of which I give a +sketch. The monk looked, and was perplexed.</p> + +<p>"Dost thou not see that the sixty-four lights add up an even number +vertically and horizontally, but that all the <i>diagonal</i> lines, except +fourteen are of a number that is odd? Why is this?"</p> + +<p>"Of a truth, my Lord Abbot, it is of the very nature of things, and +cannot be changed."</p> + +<p>"Nay, but it <i>shall</i> be changed. I command thee that certain of the +lights be closed this day, so that every line shall have an even +number of lights. See thou that this be done without delay, lest the +cellars be locked up for a month and other grievous troubles befall +thee."</p> + +<p>Father John was at his wits' end, but after consultation with one who +was learned in strange mysteries, a way was found to satisfy the whim +of the Lord Abbot. Which lights were blocked up, so that those which +remained added up an even number in every line horizontally, +vertically, and diagonally, while the least possible obstruction of +light was caused?</p> + +<hr style="width: 30%;" /> +<p><a name="X_293_THE_CHINESE_CHESSBOARD" id="X_293_THE_CHINESE_CHESSBOARD"></a><a href="#X_293_THE_CHINESE_CHESSBOARDa"><b>293.—THE CHINESE CHESSBOARD.</b></a></p> + +<p>Into how large a number of different pieces may the chessboard be cut +(by cuts along the lines only), no two pieces being exactly alike? +Remember that the arrangement of black and white constitutes a +difference. Thus, a single black square will be different from a +single white square, a row of three containing two white squares will +differ from a row of three containing two black, and so on. If two +pieces cannot be placed on the table so as to be exactly alike, they +count as different. And as the back of the board is plain, the pieces +cannot be turned over.</p> + +<hr style="width: 30%;" /> +<p><a name="X_294_THE_CHESSBOARD_SENTENCE" id="X_294_THE_CHESSBOARD_SENTENCE"></a><a href="#X_294_THE_CHESSBOARD_SENTENCEa"><b>294.—THE CHESSBOARD SENTENCE.</b></a></p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/q294.png" width="500" height="71" alt="" title="" /> +</div> + +<p>I once set myself the amusing task of so dissecting an ordinary +chessboard into letters of the alphabet that they would form a +complete sentence. It will be seen from the illustration that the +pieces assembled give the sentence, "CUT THY LIFE," with the stops +between. The ideal sentence would, of course, have only one full stop, +but that I did not succeed in obtaining.</p> + +<p>The sentence is an appeal to the transgressor to cut himself adrift +from the evil life he is living. Can you fit these pieces together to +form a perfect chessboard?</p> + + + +<hr style="width: 65%;" /><p><span class='pagenum'>Pg 88<a name="Page_88" id="Page_88"></a></span></p> +<h2><a name="STATICAL_CHESS_PUZZLES" id="STATICAL_CHESS_PUZZLES"></a><a href="#CONTENTS">STATICAL CHESS PUZZLES.</a></h2> + +<p class='center'> +"They also serve who only stand and wait."<br /> +<span style="margin-left: 8em;">MILTON.</span><br /> +</p> + +<hr style="width: 30%;" /> +<p><a name="X_295_THE_EIGHT_ROOKS" id="X_295_THE_EIGHT_ROOKS"></a><a href="#X_295_THE_EIGHT_ROOKSa"><b>295.—THE EIGHT ROOKS.</b></a></p> + + +<div class="figcenter" style="width: 400px;"> +<img src="images/q295fig1.png" width="400" height="394" alt="" title="" /> +</div> + +<p>It will be seen in the first diagram that every square on the board is +either occupied or attacked by a rook, and that every rook is +"guarded" (if they were alternately black and white rooks we should +say "attacked") by another rook. Placing the eight rooks on any row or +file obviously will have the same effect. In diagram 2 every square is +again either occupied or attacked, but in this case every rook is +unguarded. Now, in how many different ways can you so place the eight +rooks on the board that every square shall be occupied or attacked and +no rook ever guarded by another? I do not wish to go into the question +of reversals and reflections on this occasion, so that placing the +rooks on the other diagonal will count as different, and similarly +with other repetitions obtained by turning the board round.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q295fig2.png" width="400" height="391" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_296_THE_FOUR_LIONS" id="X_296_THE_FOUR_LIONS"></a><a href="#X_296_THE_FOUR_LIONSa"><b>296.—THE FOUR LIONS.</b></a></p> + +<p>The puzzle is to find in how many different ways the four lions may be +placed so that there shall never be more than one lion in any row or +column. Mere reversals and reflections will not count as different. +Thus, regarding the example given, if we place the lions in the other +diagonal, it will be considered the same arrangement. For if you hold +the second arrangement in front of a mirror or give it a quarter turn, +you merely get the first arrangement. It is a simple little puzzle, +but requires a certain amount of careful consideration.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q296.png" width="400" height="400" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_297_BISHOPSmdashUNGUARDED" id="X_297_BISHOPSmdashUNGUARDED"></a><a href="#X_297_BISHOPSmdashUNGUARDEDa"><b>297.—BISHOPS—UNGUARDED.</b></a></p> + +<p>Place as few bishops as possible on an ordinary chessboard so that +every square of the board shall be either occupied or attacked. It +will be seen that the rook has more scope than the bishop: for +wherever you place the former, it will always attack fourteen other +squares; whereas the latter will attack seven, nine, eleven, or +thirteen squares, according to the position of the diagonal on which +it is placed. And it is well here to state that when we speak of +"diagonals" in connection with the chessboard, we do not limit +ourselves to the two long diagonals from corner to corner, but include +all the shorter lines that are parallel to these. To prevent +misunderstanding on future occasions, it will be well for the reader +to note carefully this fact.</p> + +<hr style="width: 30%;" /> +<p><a name="X_298_BISHOPSmdashGUARDED" id="X_298_BISHOPSmdashGUARDED"></a><a href="#X_298_BISHOPSmdashGUARDEDa"><b>298.—BISHOPS—GUARDED.</b></a></p> + +<p>Now, how many bishops are necessary in order that every square shall +be either occupied or attacked, and every bishop guarded by another +bishop? And how may they be placed?</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 89<a name="Page_89" id="Page_89"></a></span><a name="X_299_BISHOPS_IN_CONVOCATION" id="X_299_BISHOPS_IN_CONVOCATION"></a><a href="#X_299_BISHOPS_IN_CONVOCATIONa"><b>299.—BISHOPS IN CONVOCATION.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q299.png" width="400" height="391" alt="" title="" /> +</div> + +<p>The greatest number of bishops that can be placed at the same time on +the chessboard, without any bishop attacking another, is fourteen. I +show, in diagram, the simplest way of doing this. In fact, on a square +chequered board of any number of squares the greatest number of +bishops that can be placed without attack is always two less than +twice the number of squares on the side. It is an interesting puzzle +to discover in just how many different ways the fourteen bishops may +be so placed without mutual attack. I shall give an exceedingly simple +rule for determining the number of ways for a square chequered board +of any number of squares.</p> + +<hr style="width: 30%;" /> +<p><a name="X_300_THE_EIGHT_QUEENS" id="X_300_THE_EIGHT_QUEENS"></a><a href="#X_300_THE_EIGHT_QUEENSa"><b>300.—THE EIGHT QUEENS.</b></a></p> + +<p>The queen is by far the strongest piece on the chessboard. If you +place her on one of the four squares in the centre of the board, she +attacks no fewer than twenty-seven other squares; and if you try to +hide her in a corner, she still attacks twenty-one squares. Eight +queens may be placed on the board so that no queen attacks another, +and it is an old puzzle (first proposed by Nauck in 1850, and it has +quite a little literature of its own) to discover in just how many +different ways this may be done. I show one way in the diagram, and +there are in all twelve of these fundamentally different ways. These +twelve produce ninety-two ways if we regard reversals and reflections +as different. The diagram is in a way a symmetrical arrangement. If +you turn the page upside down, it will reproduce itself exactly; but +if you look at it with one of the other sides at the bottom, you get +another way that is not identical. Then if you reflect these two ways +in a mirror you get two more ways. Now, all the other eleven solutions +are non-symmetrical, and therefore each of them may be presented in +eight ways by these reversals and reflections. It will thus be seen +why the twelve fundamentally different solutions produce only +ninety-two arrangements, as I have said, and not ninety-six, as would +happen if all twelve were non-symmetrical. It is well to have a clear +understanding on the matter of reversals and reflections when dealing +with puzzles on the chessboard.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q300.png" width="400" height="391" alt="" title="" /> +</div> + +<p>Can the reader place the eight queens on the board so that no queen +shall attack another and so that no three queens shall be in a +straight line in any oblique direction? Another glance at the diagram +will show that this arrangement will not answer the conditions, for in +the two directions indicated by the dotted lines there are three +queens in a straight line. There is only one of the twelve fundamental +ways that will solve the puzzle. Can you find it?</p> + +<hr style="width: 30%;" /> +<p><a name="X_301_THE_EIGHT_STARS" id="X_301_THE_EIGHT_STARS"></a><a href="#X_301_THE_EIGHT_STARSa"><b>301.—THE EIGHT STARS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q301.png" width="400" height="393" alt="" title="" /> +</div> + +<p>The puzzle in this case is to place eight stars in the diagram so that +no star shall be in line with another star horizontally, vertically, +or diagonally. One star is already placed, and that must not be moved, +so there are only seven for the reader now to place. But you must not +place a star on any one of the shaded squares. There is only one way +of solving this little puzzle.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 90<a name="Page_90" id="Page_90"></a></span><a name="X_302_A_PROBLEM_IN_MOSAICS" id="X_302_A_PROBLEM_IN_MOSAICS"></a><a href="#X_302_A_PROBLEM_IN_MOSAICSa"><b>302.—A PROBLEM IN MOSAICS.</b></a></p> + +<p>The art of producing pictures or designs by means of joining together +pieces of hard substances, either naturally or artificially coloured, +is of very great antiquity. It was certainly known in the time of the +Pharaohs, and we find a reference in the Book of Esther to "a pavement +of red, and blue, and white, and black marble." Some of this ancient +work that has come down to us, especially some of the Roman mosaics, +would seem to show clearly, even where design is not at first evident, +that much thought was bestowed upon apparently disorderly +arrangements. Where, for example, the work has been produced with a +very limited number of colours, there are evidences of great ingenuity +in preventing the same tints coming in close proximity. Lady readers +who are familiar with the construction of patchwork quilts will know +how desirable it is sometimes, when they are limited in the choice of +material, to prevent pieces of the same stuff coming too near +together. Now, this puzzle will apply equally to patchwork quilts or +tesselated pavements.</p> + +<p>It will be seen from the diagram how a square piece of flooring may be +paved with sixty-two square tiles of the eight colours violet, red, +yellow, green, orange, purple, white, and blue (indicated by the +initial letters), so that no tile is in line with a similarly coloured +tile, vertically, horizontally, or diagonally. Sixty-four such tiles +could not possibly be placed under these conditions, but the two +shaded squares happen to be occupied by iron ventilators.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q302.png" width="400" height="394" alt="" title="" /> +</div> + +<p>The puzzle is this. These two ventilators have to be removed to the +positions indicated by the darkly bordered tiles, and two tiles placed +in those bottom corner squares. Can you readjust the thirty-two tiles +so that no two of the same colour shall still be in line?</p> + +<hr style="width: 30%;" /> +<p><a name="X_303_UNDER_THE_VEIL" id="X_303_UNDER_THE_VEIL"></a><a href="#X_303_UNDER_THE_VEILa"><b>303.—UNDER THE VEIL.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q303.png" width="400" height="394" alt="" title="" /> +</div> + +<p>If the reader will examine the above diagram, he will see that I have +so placed eight V's, eight E's, eight I's, and eight L's in the +diagram that no letter is in line with a similar one horizontally, +vertically, or diagonally. Thus, no V is in line with another V, no E +with another E, and so on. There are a great many different ways of +arranging the letters under this condition. The puzzle is to find an +arrangement that produces the greatest possible number of four-letter +words, reading upwards and downwards, backwards and forwards, or +diagonally. All repetitions count as different words, and the five +variations that may be used are: VEIL, VILE, LEVI, LIVE, and EVIL.</p> + +<p>This will be made perfectly clear when I say that the above +arrangement scores eight, because the top and bottom row both give +VEIL; the second and seventh columns both give VEIL; and the two +diagonals, starting from the L in the 5th row and E in the 8th row, +both give LIVE and EVIL. There are therefore eight different readings +of the words in all.</p> + +<p>This difficult word puzzle is given as an example of the use of +chessboard analysis in solving such things. Only a person who is +familiar with the "Eight Queens" problem could hope to solve it.</p> + +<hr style="width: 30%;" /> +<p><a name="X_304_BACHETS_SQUARE" id="X_304_BACHETS_SQUARE"></a><a href="#X_304_BACHETS_SQUAREa"><b>304.—BACHET'S SQUARE.</b></a></p> + +<p>One of the oldest card puzzles is by Claude Caspar Bachet de Méziriac, +first published, I believe, in the 1624 edition of his work. Rearrange +the sixteen court cards (including the aces) in a square so that in no +row of four cards, horizontal, vertical, or diagonal, shall be found +two cards of the same suit or the same value. This in itself is easy +enough, but a point of the puzzle is to find in how many different +ways this may be done. The eminent French mathematician A. Labosne, in +his modern edition of Bachet, gives the answer incorrectly. And yet +the puzzle is really quite easy. Any arrangement produces seven more +by turning the square round and reflecting it in a mirror. These are +counted as different by Bachet.</p> + +<p><span class='pagenum'>Pg 91<a name="Page_91" id="Page_91"></a></span>Note "row of four cards," so that the only diagonals we have here to +consider are the two long ones.</p> + +<hr style="width: 30%;" /> +<p><a name="X_305_THE_THIRTY_SIX_LETTER_BLOCKS" id="X_305_THE_THIRTY_SIX_LETTER_BLOCKS"></a><a href="#X_305_THE_THIRTY_SIX_LETTER_BLOCKSa"><b>305.—THE THIRTY-SIX LETTER BLOCKS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q305.png" width="400" height="400" alt="" title="" /> +</div> + +<p>The illustration represents a box containing thirty-six letter-blocks. +The puzzle is to rearrange these blocks so that no A shall be in a +line vertically, horizontally, or diagonally with another A, no B with +another B, no C with another C, and so on. You will find it impossible +to get all the letters into the box under these conditions, but the +point is to place as many as possible. Of course no letters other than +those shown may be used.</p> + +<hr style="width: 30%;" /> +<p><a name="X_306_THE_CROWDED_CHESSBOARD" id="X_306_THE_CROWDED_CHESSBOARD"></a><a href="#X_306_THE_CROWDED_CHESSBOARDa"><b>306.—THE CROWDED CHESSBOARD.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q306.png" width="400" height="395" alt="" title="" /> +</div> + +<p>The puzzle is to rearrange the fifty-one pieces on the chessboard so +that no queen shall attack another queen, no rook attack another rook, +no bishop attack another bishop, and no knight attack another knight. +No notice is to be taken of the intervention of pieces of another type +from that under consideration—that is, two queens will be considered +to attack one another although there may be, say, a rook, a bishop, +and a knight between them. And so with the rooks and bishops. It is +not difficult to dispose of each type of piece separately; the +difficulty comes in when you have to find room for all the +arrangements on the board simultaneously.</p> + +<hr style="width: 30%;" /> +<p><a name="X_307_THE_COLOURED_COUNTERS" id="X_307_THE_COLOURED_COUNTERS"></a><a href="#X_307_THE_COLOURED_COUNTERSa"><b>307.—THE COLOURED COUNTERS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q307.png" width="400" height="404" alt="" title="" /> +</div> + +<p>The diagram represents twenty-five coloured counters, Red, Blue, +Yellow, Orange, and Green (indicated by their initials), and there are +five of each colour, numbered 1, 2, 3, 4, and 5. The problem is so to +place them in a square that neither colour nor number shall be found +repeated in any one of the five rows, five columns, and two diagonals. +Can you so rearrange them?</p> + +<hr style="width: 30%;" /> +<p><a name="X_308_THE_GENTLE_ART_OF_STAMP-LICKING" id="X_308_THE_GENTLE_ART_OF_STAMP-LICKING"></a><a href="#X_308_THE_GENTLE_ART_OF_STAMP-LICKINGa"><b>308.—THE GENTLE ART OF STAMP-LICKING.</b></a></p> + +<p>The Insurance Act is a most prolific source of entertaining puzzles, +particularly entertaining if you happen to be among the exempt. One's +initiation into the gentle art of stamp-licking suggests the following +little poser: If you have a card divided into sixteen spaces (4 × 4), +and are provided with plenty of stamps of the values 1<i>d</i>., 2<i>d</i>., 3<i>d</i>., +4<i>d</i>., and 5<i>d</i>., what is the greatest value that you can stick on the +card if the Chancellor of the Exchequer forbids you to place any stamp +in a straight line (that is, horizontally, vertically, or diagonally) +with another stamp of similar value? Of course, only one stamp can be +affixed in a space. The reader will probably find, when he sees the +solution, that, like the stamps themselves, he is licked <span class='pagenum'>Pg 92<a name="Page_92" id="Page_92"></a></span>He will most +likely be twopence short of the maximum. A friend asked the Post +Office how it was to be done; but they sent him to the Customs and +Excise officer, who sent him to the Insurance Commissioners, who sent +him to an approved society, who profanely sent him—but no matter.</p> + +<hr style="width: 30%;" /> +<p><a name="X_309_THE_FORTY-NINE_COUNTERS" id="X_309_THE_FORTY-NINE_COUNTERS"></a><a href="#X_309_THE_FORTY-NINE_COUNTERSa"><b>309.—THE FORTY-NINE COUNTERS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q309.png" width="400" height="401" alt="" title="" /> +</div> + +<p>Can you rearrange the above forty-nine counters in a square so that no +letter, and also no number, shall be in line with a similar one, +vertically, horizontally, or diagonally? Here I, of course, mean in +the lines parallel with the diagonals, in the chessboard sense.</p> + +<hr style="width: 30%;" /> +<p><a name="X_310_THE_THREE_SHEEP" id="X_310_THE_THREE_SHEEP"></a><a href="#X_310_THE_THREE_SHEEPa"><b>310.—THE THREE SHEEP.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q310.png" width="400" height="398" alt="" title="" /> +</div> + +<p>A farmer had three sheep and an arrangement of sixteen pens, divided +off by hurdles in the manner indicated in the illustration. In how +many different ways could he place those sheep, each in a separate +pen, so that every pen should be either occupied or in line +(horizontally, vertically, or diagonally) with at least one sheep? I +have given one arrangement that fulfils the conditions. How many +others can you find? Mere reversals and reflections must not be +counted as different. The reader may regard the sheep as queens. The +problem is then to place the three queens so that every square shall +be either occupied or attacked by at least one queen—in the maximum +number of different ways.</p> + +<hr style="width: 30%;" /> +<p><a name="X_311_THE_FIVE_DOGS_PUZZLE" id="X_311_THE_FIVE_DOGS_PUZZLE"></a><a href="#X_311_THE_FIVE_DOGS_PUZZLEa"><b>311.—THE FIVE DOGS PUZZLE.</b></a></p> + +<p>In 1863, C.F. de Jaenisch first discussed the "Five Queens Puzzle"—to +place five queens on the chessboard so that every square shall be +attacked or occupied—which was propounded by his friend, a "Mr. de +R." Jaenisch showed that if no queen may attack another there are +ninety-one different ways of placing the five queens, reversals and +reflections not counting as different. If the queens may attack one +another, I have recorded hundreds of ways, but it is not practicable +to enumerate them exactly.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q311.png" width="400" height="398" alt="" title="" /> +</div> + +<p>The illustration is supposed to represent an arrangement of sixty-four +kennels. It will be seen that five kennels each contain a dog, and on +further examination it will be seen that every one of the sixty-four +kennels is in a straight line with at least one dog—either +horizontally, vertically, or diagonally. Take any kennel you like, and +you will find that you can draw a straight line to a dog in one or +other of the three ways mentioned. The puzzle is to replace the five +dogs and discover in just how many different ways they may be placed +in five kennels <i>in a straight row</i>, so that every kennel shall always +be in line with at least one dog. Reversals and reflections are here +counted as different.</p> + +<hr style="width: 30%;" /> +<p><a name="X_312_THE_FIVE_CRESCENTS_OF_BYZANTIUM" id="X_312_THE_FIVE_CRESCENTS_OF_BYZANTIUM"></a><a href="#X_312_THE_FIVE_CRESCENTS_OF_BYZANTIUMa"><b>312.—THE FIVE CRESCENTS OF BYZANTIUM.</b></a></p> + +<p>When Philip of Macedon, the father of Alexander the Great, found +himself confronted with great difficulties in the siege of Byzantium, +he <span class='pagenum'>Pg 93<a name="Page_93" id="Page_93"></a></span>set his men to undermine the walls. His desires, however, +miscarried, for no sooner had the operations been begun than a +crescent moon suddenly appeared in the heavens and discovered his +plans to his adversaries. The Byzantines were naturally elated, and in +order to show their gratitude they erected a statue to Diana, and the +crescent became thenceforward a symbol of the state. In the temple +that contained the statue was a square pavement composed of sixty-four +large and costly tiles. These were all plain, with the exception of +five, which bore the symbol of the crescent. These five were for +occult reasons so placed that every tile should be watched over by +(that is, in a straight line, vertically, horizontally, or diagonally +with) at least one of the crescents. The arrangement adopted by the +Byzantine architect was as follows:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q312.png" width="400" height="402" alt="" title="" /> +</div> + +<p>Now, to cover up one of these five crescents was a capital offence, +the death being something very painful and lingering. But on a certain +occasion of festivity it was necessary to lay down on this pavement a +square carpet of the largest dimensions possible, and I have shown in +the illustration by dark shading the largest dimensions that would be +available.</p> + +<p>The puzzle is to show how the architect, if he had foreseen this +question of the carpet, might have so arranged his five crescent tiles +in accordance with the required conditions, and yet have allowed for +the largest possible square carpet to be laid down without any one of +the five crescent tiles being covered, or any portion of them.</p> + +<hr style="width: 30%;" /> +<p><a name="X_313_QUEENS_AND_BISHOP_PUZZLE" id="X_313_QUEENS_AND_BISHOP_PUZZLE"></a><a href="#X_313_QUEENS_AND_BISHOP_PUZZLEa"><b>313.—QUEENS AND BISHOP PUZZLE.</b></a></p> + +<p>It will be seen that every square of the board is either occupied or +attacked. The puzzle is to substitute a bishop for the rook on the +same square, and then place the four queens on other squares so that +every square shall again be either occupied or attacked.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q313.png" width="400" height="412" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_314_THE_SOUTHERN_CROSS" id="X_314_THE_SOUTHERN_CROSS"></a><a href="#X_314_THE_SOUTHERN_CROSSa"><b>314.—THE SOUTHERN CROSS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q314.png" width="400" height="392" alt="" title="" /> +</div> + +<p>In the above illustration we have five Planets and eighty-one Fixed +Stars, five of the latter being hidden by the Planets. It will be +found that every Star, with the exception of the ten that have a black +spot in their centres, is in a straight line, vertically, +horizontally, or diagonally, with at least one of the Planets. The +puzzle is so to rearrange the Planets that all the Stars shall be in +line with one or more of them.</p> + +<p>In rearranging the Planets, each of the five may be moved once in a +straight line, in either of the three directions mentioned. They will, +of course, obscure five other Stars in place of those at present +covered.</p> + +<hr style="width: 30%;" /> +<p><a name="X_315_THE_HAT-PEG_PUZZLE" id="X_315_THE_HAT-PEG_PUZZLE"></a><a href="#X_315_THE_HAT-PEG_PUZZLEa"><b>315.—THE HAT-PEG PUZZLE.</b></a></p> + +<p>Here is a five-queen puzzle that I gave in a fanciful dress in 1897. +As the queens were <span class='pagenum'>Pg 94<a name="Page_94" id="Page_94"></a></span>there represented as hats on sixty-four pegs, I +will keep to the title, "The Hat-Peg Puzzle." It will be seen that +every square is occupied or attacked. The puzzle is to remove one +queen</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q315.png" width="400" height="396" alt="" title="" /> +</div> + +<p>to a different square so that still every square is occupied or +attacked, then move a second queen under a similar condition, then a +third queen, and finally a fourth queen. After the fourth move every +square must be attacked or occupied, but no queen must then attack +another. Of course, the moves need not be "queen moves;" you can move +a queen to any part of the board.</p> + +<hr style="width: 30%;" /> +<p><a name="X_316_THE_AMAZONS" id="X_316_THE_AMAZONS"></a><a href="#X_316_THE_AMAZONSa"><b>316.—THE AMAZONS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q316.png" width="400" height="402" alt="" title="" /> +</div> + +<p>This puzzle is based on one by Captain Turton. Remove three of the +queens to other squares so that there shall be eleven squares on the +board that are not attacked. The removal of the three queens need not +be by "queen moves." You may take them up and place them anywhere. +There is only one solution.</p> + +<hr style="width: 30%;" /> +<p><a name="X_317_A_PUZZLE_WITH_PAWNS" id="X_317_A_PUZZLE_WITH_PAWNS"></a><a href="#X_317_A_PUZZLE_WITH_PAWNSa"><b>317.—A PUZZLE WITH PAWNS.</b></a></p> + +<p>Place two pawns in the middle of the chessboard, one at Q 4 and the +other at K 5. Now, place the remaining fourteen pawns (sixteen in all) +so that no three shall be in a straight line in any possible +direction.</p> + +<p>Note that I purposely do not say queens, because by the words "any +possible direction" I go beyond attacks on diagonals. The pawns must +be regarded as mere points in space—at the centres of the squares. +See dotted lines in the case of No. <a href="#X_300_THE_EIGHT_QUEENS">300</a>, "<a href="#X_300_THE_EIGHT_QUEENS">The Eight Queens</a>."</p> + +<hr style="width: 30%;" /> +<p><a name="X_318_LION-HUNTING" id="X_318_LION-HUNTING"></a><a href="#X_318_LION-HUNTINGa"><b>318.—LION-HUNTING.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q318.png" width="400" height="402" alt="" title="" /> +</div> + +<p>My friend Captain Potham Hall, the renowned hunter of big game, says +there is nothing more exhilarating than a brush with a herd—a +pack—a team—a flock—a swarm (it has taken me a full quarter of an +hour to recall the right word, but I have it at last)—a <i>pride</i> of +lions. Why a number of lions are called a "pride," a number of whales +a "school," and a number of foxes a "skulk" are mysteries of philology +into which I will not enter.</p> + +<p>Well, the captain says that if a spirited lion crosses your path in +the desert it becomes lively, for the lion has generally been looking +for the man just as much as the man has sought the king of the forest. +And yet when they meet they always quarrel and fight it out. A little +contemplation of this unfortunate and long-standing feud between two +estimable families has led me to figure out a few calculations as to +the probability of the man and the lion crossing one another's path in +the jungle. In all these cases one has to start on certain more <span class='pagenum'>Pg 95<a name="Page_95" id="Page_95"></a></span>or +less arbitrary assumptions. That is why in the above illustration I +have thought it necessary to represent the paths in the desert with +such rigid regularity. Though the captain assures me that the tracks +of the lions usually run much in this way, I have doubts.</p> + +<p>The puzzle is simply to find out in how many different ways the man +and the lion may be placed on two different spots that are not on the +same path. By "paths" it must be understood that I only refer to the +ruled lines. Thus, with the exception of the four corner spots, each +combatant is always on two paths and no more. It will be seen that +there is a lot of scope for evading one another in the desert, which +is just what one has always understood.</p> + +<hr style="width: 30%;" /> +<p><a name="X_319_THE_KNIGHT-GUARDS" id="X_319_THE_KNIGHT-GUARDS"></a><a href="#X_319_THE_KNIGHT-GUARDSa"><b>319.—THE KNIGHT-GUARDS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q319.png" width="400" height="398" alt="" title="" /> +</div> + +<p>The knight is the irresponsible low comedian of the chessboard. "He is +a very uncertain, sneaking, and demoralizing rascal," says an American +writer. "He can only move two squares, but makes up in the quality of +his locomotion for its quantity, for he can spring one square sideways +and one forward simultaneously, like a cat; can stand on one leg in +the middle of the board and jump to any one of eight squares he +chooses; can get on one side of a fence and blackguard three or four +men on the other; has an objectionable way of inserting himself in +safe places where he can scare the king and compel him to move, and +then gobble a queen. For pure cussedness the knight has no equal, and +when you chase him out of one hole he skips into another." Attempts +have been made over and over again to obtain a short, simple, and +exact definition of the move of the knight—without success. It really +consists in moving one square like a rook, and then another square +like a bishop—the two operations being done in one leap, so that it +does not matter whether the first square passed over is occupied by +another piece or not. It is, in fact, the only leaping move in chess. +But difficult as it is to define, a child can learn it by inspection +in a few minutes.</p> + +<p>I have shown in the diagram how twelve knights (the fewest possible +that will perform the feat) may be placed on the chessboard so that +every square is either occupied or attacked by a knight. Examine every +square in turn, and you will find that this is so. Now, the puzzle in +this case is to discover what is the smallest possible number of +knights that is required in order that every square shall be either +occupied or attacked, and every knight protected by another knight. +And how would you arrange them? It will be found that of the twelve +shown in the diagram only four are thus protected by being a knight's +move from another knight.</p> + + +<h2><a name="THE_GUARDED_CHESSBOARD" id="THE_GUARDED_CHESSBOARD"></a><a href="#CONTENTS">THE GUARDED CHESSBOARD.</a></h2> + +<p>On an ordinary chessboard, 8 by 8, every square can be guarded—that +is, either occupied or attacked—by 5 queens, the fewest possible. +There are exactly 91 fundamentally different arrangements in which no +queen attacks another queen. If every queen must attack (or be +protected by) another queen, there are at fewest 41 arrangements, and +I have recorded some 150 ways in which some of the queens are attacked +and some not, but this last case is very difficult to enumerate +exactly.</p> + +<p>On an ordinary chessboard every square can be guarded by 8 rooks (the +fewest possible) in 40,320 ways, if no rook may attack another rook, +but it is not known how many of these are fundamentally different. +(See solution to No. <a href="#X_295_THE_EIGHT_ROOKSa">295</a>, "<a href="#X_295_THE_EIGHT_ROOKSa">The Eight Rooks</a>.") I have not enumerated +the ways in which every rook shall be protected by another rook.</p> + +<p>On an ordinary chessboard every square can be guarded by 8 bishops +(the fewest possible), if no bishop may attack another bishop. Ten +bishops are necessary if every bishop is to be protected. (See Nos. +<a href="#X_297_BISHOPSmdashUNGUARDED">297</a> and <a href="#X_298_BISHOPSmdashGUARDED">298</a>, "<a href="#X_297_BISHOPSmdashUNGUARDED">Bishops unguarded</a>" and "<a href="#X_298_BISHOPSmdashGUARDED">Bishops guarded</a>.")</p> + +<p>On an ordinary chessboard every square can be guarded by 12 knights if +all but 4 are unprotected. But if every knight must be protected, 14 +are necessary. (See No. <a href="#X_319_THE_KNIGHT-GUARDS">319</a>, "<a href="#X_319_THE_KNIGHT-GUARDS">The Knight-Guards</a>.")</p> + +<p>Dealing with the queen on <i>n</i><sup>2</sup> boards generally, where <i>n</i> is less +than 8, the following results will be of interest:—</p> + + +<p>1 queen guards 2<sup>2</sup> board in 1 fundamental way.</p> + +<p>1 queen guards 3<sup>2</sup> board in 1 fundamental way.</p> + +<p>2 queens guard 4<sup>2</sup> board in 3 fundamental ways (protected).</p> + +<p>3 queens guard 4<sup>2</sup> board in 2 fundamental ways (not protected).</p> + +<p>3 queens guard 5<sup>2</sup> board in 37 fundamental ways (protected).</p> + +<p>3 queens guard 5<sup>2</sup> board in 2 fundamental ways (not protected).</p> + +<p>3 queens guard 6<sup>2</sup> board in 1 fundamental way (protected).</p><p><span class='pagenum'>Pg 96<a name="Page_96" id="Page_96"></a></span></p> + +<p>4 queens guard 6<sup>2</sup> board in 17 fundamental ways (not protected).</p> + +<p>4 queens guard 7<sup>2</sup> board in 5 fundamental ways (protected).</p> + +<p>4 queens guard 7<sup>2</sup> board in 1 fundamental way (not protected).</p> + + +<h3>NON-ATTACKING CHESSBOARD ARRANGEMENTS.</h3> + +<p>We know that n queens may always be placed on a square board of n<sup>2</sup> +squares (if n be greater than 3) without any queen attacking another +queen. But no general formula for enumerating the number of different +ways in which it may be done has yet been discovered; probably it is +undiscoverable. The known results are as follows:—</p> + +<p>Where n = 4 there is 1 fundamental solution and 2 in all.</p> + +<p>Where n = 5 there are 2 fundamental solutions and 10 in all.</p> + +<p>Where n = 6 there is 1 fundamental solution and 4 in all.</p> + +<p>Where n = 7 there are 6 fundamental solutions and 40 in all.</p> + +<p>Where n = 8 there are 12 fundamental solutions and 92 in all.</p> + +<p>Where n = 9 there are 46 fundamental solutions.</p> + +<p>Where n = 10 there are 92 fundamental solutions.</p> + +<p>Where n = 11 there are 341 fundamental solutions.</p> + +<p>Obviously n rooks may be placed without attack on an n<sup>2</sup> board in n! +ways, but how many of these are fundamentally different I have only +worked out in the four cases where n equals 2, 3, 4, and 5. The +answers here are respectively 1, 2, 7, and 23. (See No. <a href="#X_296_THE_FOUR_LIONS">296</a>, "<a href="#X_296_THE_FOUR_LIONS">The Four +Lions</a>.")</p> + +<p>We can place 2n-2 bishops on an n<sup>2</sup> board in 2<sup>n</sup> ways. (See No. +<a href="#X_299_BISHOPS_IN_CONVOCATION">299</a>, "<a href="#X_299_BISHOPS_IN_CONVOCATION">Bishops in Convocation</a>.") For boards containing 2, 3, 4, 5, 6, +7, 8 squares, on a side there are respectively 1, 2, 3, 6, 10, 20, 36 +fundamentally different arrangements. Where n is odd there are +2<sup>½(n-1)</sup> such arrangements, each giving 4 by reversals and +reflections, and 2<sup>n-3</sup> - 2<sup>½(n-3)</sup> giving 8. Where n is even there +are 2<sup>½(n-2)</sup>, each giving 4 by reversals and reflections, and +2<sup>n-3</sup> - 2<sup>½(n-4)</sup>, each giving 8.</p> + +<p>We can place ½(n<sup>2</sup>+1) knights on an n<sup>2</sup> board without attack, when +n is odd, in 1 fundamental way; and ½n<sup>2</sup> knights on an n<sup>2</sup> board, +when n is even, in 1 fundamental way. In the first case we place all +the knights on the same colour as the central square; in the second +case we place them all on black, or all on white, squares.</p> + + +<h3>THE TWO PIECES PROBLEM.</h3> + +<p>On a board of n<sup>2</sup> squares, two queens, two rooks, two bishops, or +two knights can always be placed, irrespective of attack or not, in +½(n<sup>4</sup> - n<sup>2</sup>) ways. The following formulæ will show in how many of +these ways the two pieces may be placed with attack and without:—</p> + +<div class='center'> +<table border="0" cellpadding="1" cellspacing="3" summary=""> +<tr><td align='left'></td><td align='center'>With Attack.</td><td align='center'>Without Attack.</td></tr> +<tr><td align='left' rowspan='2'>2 Queens</td><td align='center' class='bb'>5n3 - 6n2 + n</td><td align='center' class='bb'>3n4 - 10n3 + 9n2 - 2n</td></tr> +<tr><td align='center'>3</td><td align='center'>6</td></tr> +<tr><td align='left' rowspan='2'>2 Rooks</td><td align='center' rowspan='2'>n3 - n2</td><td align='center' class='bb'>n4 - 2n3 + n2</td></tr> +<tr><td align='center'>2</td></tr> +<tr><td align='left' rowspan='2'>2 Bishops</td><td align='center' class='bb'>4n3 - 6n2 + 2n</td><td align='center' class='bb'>3n4 - 4n3 + 3n2 - 2n</td></tr> +<tr><td align='center'>6</td><td align='center'>6</td></tr> +<tr><td align='left' rowspan='2'>2 Knights</td><td align='center' rowspan='2'>4n2 - 12n + 8</td><td align='center' class='bb'>n4 - 9n2 + 24n</td></tr> +<tr><td align='center'>2</td></tr> +</table></div> + +<p>(See No. <a href="#X_318_LION-HUNTING">318</a>, "<a href="#X_318_LION-HUNTING">Lion Hunting</a>.")</p> + + +<hr style="width: 65%;" /> +<h2><a name="DYNAMICAL_CHESS_PUZZLES" id="DYNAMICAL_CHESS_PUZZLES"></a><a href="#CONTENTS">DYNAMICAL CHESS PUZZLES.</a></h2> + +<p class='center'> +<span style="margin-left: 0em;">"Push on—keep moving."<br /></span> +<span style="margin-left: 8em;">THOS. MORTON: <i>Cure for the Heartache</i>.</span><br /> +</p> + +<hr style="width: 30%;" /> +<p><a name="X_320_THE_ROOKS_TOUR" id="X_320_THE_ROOKS_TOUR"></a><a href="#X_320_THE_ROOKS_TOURa"><b>320.—THE ROOK'S TOUR.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q320.png" width="400" height="397" alt="" title="" /> +</div> + + +<p>The puzzle is to move the single rook over the whole board, so that it +shall visit every square of the board once, and only once, and end its +tour on the square from which it starts. You have to do this in as few +moves as possible, and unless you are very careful you will take just +one move too many. Of course, a square is regarded equally as +"visited" whether you merely pass over it or make it a stopping-place, +and we will not quibble over the point whether the original square is +actually visited twice. We will assume that it is not.</p> + +<hr style="width: 30%;" /> +<p><a name="X_321_THE_ROOKS_JOURNEY" id="X_321_THE_ROOKS_JOURNEY"></a><a href="#X_321_THE_ROOKS_JOURNEYa"><b>321.—THE ROOK'S JOURNEY.</b></a></p> + +<p>This puzzle I call "The Rook's Journey," because the word "tour" +(derived from a turner's wheel) implies that we return to the point +from which we set out, and we do not do this in the present case. We +should not be satisfied with <span class='pagenum'>Pg 97<a name="Page_97" id="Page_97"></a></span>a personally conducted holiday tour that +ended by leaving us, say, in the middle of the Sahara. The rook here +makes twenty-one moves, in the course of which journey it visits every +square of the board once and only once, stopping at the square marked +10 at the end of its tenth move, and ending at the square marked 21. +Two consecutive moves cannot be made in the same direction—that is to +say, you must make a turn after every move.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q321.png" width="400" height="392" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_322_THE_LANGUISHING_MAIDEN" id="X_322_THE_LANGUISHING_MAIDEN"></a><a href="#X_322_THE_LANGUISHING_MAIDENa"><b>322.—THE LANGUISHING MAIDEN.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q322.png" width="400" height="393" alt="" title="" /> +</div> + +<p>A wicked baron in the good old days imprisoned an innocent maiden in +one of the deepest dungeons beneath the castle moat. It will be seen +from our illustration that there were sixty-three cells in the +dungeon, all connected by open doors, and the maiden was chained in +the cell in which she is shown. Now, a valiant knight, who loved the +damsel, succeeded in rescuing her from the enemy. Having gained an +entrance to the dungeon at the point where he is seen, he succeeded in +reaching the maiden after entering every cell once and only once. Take +your pencil and try to trace out such a route. When you have +succeeded, then try to discover a route in twenty-two straight paths +through the cells. It can be done in this number without entering any +cell a second time.</p> + +<hr style="width: 30%;" /> +<p><a name="X_323_A_DUNGEON_PUZZLE" id="X_323_A_DUNGEON_PUZZLE"></a><a href="#X_323_A_DUNGEON_PUZZLEa"><b>323.—A DUNGEON PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q323.png" width="400" height="394" alt="" title="" /> +</div> + +<p>A French prisoner, for his sins (or other people's), was confined in +an underground dungeon containing sixty-four cells, all communicating +with open doorways, as shown in our illustration. In order to reduce +the tedium of his restricted life, he set himself various puzzles, and +this is one of them. Starting from the cell in which he is shown, how +could he visit every cell once, and only once, and make as many +turnings as possible? His first attempt is shown by the dotted track. +It will be found that there are as many as fifty-five straight lines +in his path, but after many attempts he improved upon this. Can you +get more than fifty-five? You may end your path in any cell you like. +Try the puzzle with a pencil on chessboard diagrams, or you may regard +them as rooks' moves on a board.</p> + +<hr style="width: 30%;" /> +<p><a name="X_324_THE_LION_AND_THE_MAN" id="X_324_THE_LION_AND_THE_MAN"></a><a href="#X_324_THE_LION_AND_THE_MANa"><b>324.—THE LION AND THE MAN.</b></a></p> + +<p>In a public place in Rome there once stood a prison divided into +sixty-four cells, all open to the sky and all communicating with one +another, as shown in the illustration. The sports that here took place +were watched from a high tower. The favourite game was to place a +Christian in one corner cell and a lion in the diagonally opposite +corner and then leave them with all the inner doors open. The +consequent effect was sometimes most laughable. On one occasion the +man was given a sword. He was <span class='pagenum'>Pg 98<a name="Page_98" id="Page_98"></a></span>no coward, and was as anxious to find +the lion as the lion undoubtedly was to find him.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q324.png" width="400" height="390" alt="" title="" /> +</div> + +<p>The man visited every cell once and only once in the fewest possible +straight lines until he reached the lion's cell. The lion, curiously +enough, also visited every cell once and only once in the fewest +possible straight lines until he finally reached the man's cell. They +started together and went at the same speed; yet, although they +occasionally got glimpses of one another, they never once met. The +puzzle is to show the route that each happened to take.</p> + +<hr style="width: 30%;" /> +<p><a name="X_325_AN_EPISCOPAL_VISITATION" id="X_325_AN_EPISCOPAL_VISITATION"></a><a href="#X_325_AN_EPISCOPAL_VISITATIONa"><b>325.—AN EPISCOPAL VISITATION.</b></a></p> + +<p>The white squares on the chessboard represent the parishes of a +diocese. Place the bishop on any square you like, and so contrive that +(using the ordinary bishop's move of chess) he shall visit every one +of his parishes in the fewest possible moves. Of course, all the +parishes passed through on any move are regarded as "visited." You can +visit any squares more than once, but you are not allowed to move +twice between the same two adjoining squares. What are the fewest +possible moves? The bishop need not end his visitation at the parish +from which he first set out.</p> + +<hr style="width: 30%;" /> +<p><a name="X_326_A_NEW_COUNTER_PUZZLE" id="X_326_A_NEW_COUNTER_PUZZLE"></a><a href="#X_326_A_NEW_COUNTER_PUZZLEa"><b>326.—A NEW COUNTER PUZZLE.</b></a></p> + +<p>Here is a new puzzle with moving counters, or coins, that at first +glance looks as if it must be absurdly simple. But it will be found +quite a little perplexity. I give it in this place for a reason that I +will explain when we come to the next puzzle. Copy the simple diagram, +enlarged, on a sheet of paper; then place two white counters on the +points 1 and 2, and two red counters on 9 and 10, The puzzle is to +make the red and white change places. You may move the counters one at +a time in any order you like, along the lines from point to point, +with the only restriction that a red and a white counter may never +stand at once on the same straight line. Thus the first move can only +be from 1 or 2 to 3, or from 9 or 10 to 7.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q326.png" width="400" height="307" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_327_A_NEW_BISHOPS_PUZZLE" id="X_327_A_NEW_BISHOPS_PUZZLE"></a><a href="#X_327_A_NEW_BISHOPS_PUZZLEa"><b>327.—A NEW BISHOP'S PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q327.png" width="400" height="493" alt="" title="" /> +</div> + +<p>This is quite a fascinating little puzzle. Place eight bishops (four +black and four white) on the reduced chessboard, as shown in the +illustration. The problem is to make the black bishops change places +with the white ones, no bishop ever attacking another of the opposite +colour. They must move alternately—first a white, then a black, then +a white, and so on. When you have succeeded in doing it at all, try to +find the fewest possible moves.</p> + +<p>If you leave out the bishops standing on black squares, and only play +on the white squares, you will discover my last puzzle turned on its +side.</p> + +<hr style="width: 30%;" /> +<p><a name="X_328_THE_QUEENS_TOUR" id="X_328_THE_QUEENS_TOUR"></a><a href="#X_328_THE_QUEENS_TOURa"><b>328.—THE QUEEN'S TOUR.</b></a></p> + +<p>The puzzle of making a complete tour of the chessboard with the queen +in the fewest possible moves (in which squares may be visited more +than once) was first given by the late Sam Loyd <span class='pagenum'>Pg 99<a name="Page_99" id="Page_99"></a></span>in his <i>Chess +Strategy</i>. But the solution shown below is the one he gave in +<i>American Chess-Nuts</i> in 1868. I have recorded at least six different +solutions in the minimum number of moves—fourteen—but this one is +the best of all, for reasons I will explain.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q328a.png" width="400" height="397" alt="" title="" /> +</div> + +<p>If you will look at the lettered square you will understand that there +are only ten really differently placed squares on a chessboard—those +enclosed by a dark line—all the others are mere reversals or +reflections. For example, every A is a corner square, and every J a +central square. Consequently, as the solution shown has a +turning-point at the enclosed D square, we can obtain a solution +starting from and ending at any square marked D—by just turning the +board about. Now, this scheme will give you a tour starting from any +A, B, C, D, E, F, or H, while no other route that I know can be +adapted to more than five different starting-points. There is no +Queen's Tour in fourteen moves (remember a tour must be re-entrant) +that may start from a G, I, or J. But we can have a non-re-entrant +path over the whole board in fourteen moves, starting from any given +square. Hence the following puzzle:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q328b.png" width="400" height="397" alt="" title="" /> +</div> + +<p>Start from the J in the enclosed part of the lettered diagram and +visit every square of the board in fourteen moves, ending wherever you +like.</p> + +<hr style="width: 30%;" /> +<p><a name="X_329_THE_STAR_PUZZLE" id="X_329_THE_STAR_PUZZLE"></a><a href="#X_329_THE_STAR_PUZZLEa"><b>329.—THE STAR PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q329.png" width="400" height="401" alt="" title="" /> +</div> + +<p>Put the point of your pencil on one of the white stars and (without +ever lifting your pencil from the paper) strike out all the stars in +fourteen continuous straight strokes, ending at the second white star. +Your straight strokes may be in any direction you like, only every +turning must be made on a star. There is no objection to striking out +any star more than once.</p> + +<p>In this case, where both your starting and ending squares are fixed +inconveniently, you cannot obtain a solution by breaking a Queen's +Tour, or in any other way by queen moves alone. But you are allowed to +use oblique straight lines—such as from the upper white star direct +to a corner star.</p> + +<hr style="width: 30%;" /> +<p><a name="X_330_THE_YACHT_RACE" id="X_330_THE_YACHT_RACE"></a><a href="#X_330_THE_YACHT_RACEa"><b>330.—THE YACHT RACE.</b></a></p> + +<p>Now then, ye land-lubbers, hoist your baby-jib-topsails, break out +your spinnakers, ease off your balloon sheets, and get your head-sails +set!</p> + +<p>Our race consists in starting from the point at which the yacht is +lying in the illustration and touching every one of the sixty-four +buoys in fourteen straight courses, returning in the final tack to the +buoy from which we start. The seventh course must finish at the buoy +from which a flag is flying.</p> + +<p>This puzzle will call for a lot of skilful seamanship on account of +the sharp angles at which it will occasionally be necessary to tack. +<span class='pagenum'>Pg 100<a name="Page_100" id="Page_100"></a></span>The point of a lead pencil and a good nautical eye are all the outfit +that we require.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q330.png" width="400" height="342" alt="" title="" /> +</div> + +<p>This is difficult, because of the condition as to the flag-buoy, and +because it is a re-entrant tour. But again we are allowed those +oblique lines.</p> + +<hr style="width: 30%;" /> +<p><a name="X_331_THE_SCIENTIFIC_SKATER" id="X_331_THE_SCIENTIFIC_SKATER"></a><a href="#X_331_THE_SCIENTIFIC_SKATERa"><b>331.—THE SCIENTIFIC SKATER.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q331.png" width="400" height="467" alt="" title="" /> +</div> + +<p>It will be seen that this skater has marked on the ice sixty-four +points or stars, and he proposes to start <i>from his present position</i> +near the corner and enter every one of the points in fourteen straight +lines. How will he do it? Of course there is no objection to his +passing over any point more than once, but his last straight stroke +must bring him back to the position from which he started.</p> + +<p>It is merely a matter of taking your pencil and starting from the spot +on which the skater's foot is at present resting, and striking out all +the stars in fourteen continuous straight lines, returning to the +point from which you set out.</p> + +<hr style="width: 30%;" /> +<p><a name="X_332_THE_FORTY-NINE_STARS" id="X_332_THE_FORTY-NINE_STARS"></a><a href="#X_332_THE_FORTY-NINE_STARSa"><b>332.—THE FORTY-NINE STARS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q332.png" width="400" height="383" alt="" title="" /> +</div> + +<p>The puzzle in this case is simply to take your pencil and, starting +from one black star, strike out all the stars in twelve straight +strokes, ending at the other black star. It will be seen that the +attempt shown in the illustration requires fifteen strokes. Can you do +it in twelve? Every turning must be made on a star, and the lines must +be parallel to the sides and diagonals of the square, as shown. In +this case we are dealing with a chessboard of reduced dimensions, but +only queen moves (without going outside the boundary as in the last +case) are required.</p> + +<hr style="width: 30%;" /> +<p><a name="X_333_THE_QUEENS_JOURNEY" id="X_333_THE_QUEENS_JOURNEY"></a><a href="#X_333_THE_QUEENS_JOURNEYa"><b>333.—THE QUEEN'S JOURNEY.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q333.png" width="400" height="403" alt="" title="" /> +</div> + +<p>Place the queen on her own square, as shown in the illustration, and +then try to discover the <span class='pagenum'>Pg 101<a name="Page_101" id="Page_101"></a></span>greatest distance that she can travel over +the board in five queen's moves without passing over any square a +second time. Mark the queen's path on the board, and note carefully +also that she must never cross her own track. It seems simple enough, +but the reader may find that he has tripped.</p> + +<hr style="width: 30%;" /> +<p><a name="X_334_ST_GEORGE_AND_THE_DRAGON" id="X_334_ST_GEORGE_AND_THE_DRAGON"></a><a href="#X_334_ST_GEORGE_AND_THE_DRAGONa"><b>334.—ST. GEORGE AND THE DRAGON.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q334.png" width="400" height="400" alt="" title="" /> +</div> + +<p>Here is a little puzzle on a reduced chessboard of forty-nine squares. +St. George wishes to kill the dragon. Killing dragons was a well-known +pastime of his, and, being a knight, it was only natural that he +should desire to perform the feat in a series of knight's moves. Can +you show how, starting from that central square, he may visit once, +and only once, every square of the board in a chain of chess knight's +moves, and end by capturing the dragon on his last move? Of course a +variety of different ways are open to him, so try to discover a route +that forms some pretty design when you have marked each successive +leap by a straight line from square to square.</p> + +<hr style="width: 30%;" /> +<p><a name="X_335_FARMER_LAWRENCES_CORNFIELDS" id="X_335_FARMER_LAWRENCES_CORNFIELDS"></a><a href="#X_335_FARMER_LAWRENCES_CORNFIELDSa"><b>335.—FARMER LAWRENCE'S CORNFIELDS.</b></a></p> + +<p>One of the most beautiful districts within easy distance of London for +a summer ramble is that part of Buckinghamshire known as the Valley of +the Chess—at least, it was a few years ago, before it was discovered +by the speculative builder. At the beginning of the present century +there lived, not far from Latimers, a worthy but eccentric farmer +named Lawrence. One of his queer notions was that every person who +lived near the banks of the river Chess ought to be in some way +acquainted with the noble game of the same name, and in order to +impress this fact on his men and his neighbours he adopted at times +strange terminology. For example, when one of his ewes presented him +with a lamb, he would say that it had "queened a pawn"; when he put up +a new barn against the highway, he called it "castling on the king's +side"; and when he sent a man with a gun to keep his neighbour's birds +off his fields, he spoke of it as "attacking his opponent's rooks." +Everybody in the neighbourhood used to be amused at Farmer Lawrence's +little jokes, and one boy (the wag of the village) who got his ears +pulled by the old gentleman for stealing his "chestnuts" went so far +as to call him "a silly old chess-protector!"</p> + +<p>One year he had a large square field divided into forty-nine square +plots, as shown in the illustration. The white squares were sown with +wheat and the black squares with barley. When the harvest time came +round he gave orders that his men were first to cut the corn in the +patch marked 1, and that each successive cutting should be exactly a +knight's move from the last one, the thirteenth cutting being in the +patch marked 13, the twenty-fifth in the patch marked 25, the +thirty-seventh in the one marked 37, and the last, or forty-ninth +cutting, in the patch marked 49. This was too much for poor Hodge, and +each day Farmer Lawrence had to go down to the field and show which +piece had to be operated upon. But the problem will perhaps present no +difficulty to my readers.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q335.png" width="400" height="448" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_336_THE_GREYHOUND_PUZZLE" id="X_336_THE_GREYHOUND_PUZZLE"></a><a href="#X_336_THE_GREYHOUND_PUZZLEa"><b>336.—THE GREYHOUND PUZZLE.</b></a></p> + +<p>In this puzzle the twenty kennels do not communicate with one another +by doors, but are divided off by a low wall. The solitary occupant is +the greyhound which lives in the kennel in the top left-hand corner. +When he is allowed his liberty he has to obtain it by visiting every +kennel once and only once in a series of knight's <span class='pagenum'>Pg 102<a name="Page_102" id="Page_102"></a></span>moves, ending at +the bottom right-hand corner, which is open to the world. The lines in +the above diagram show one solution. The puzzle is to discover in how +many different ways the greyhound may thus make his exit from his +corner kennel.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q336.png" width="400" height="325" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_337_THE_FOUR_KANGAROOS" id="X_337_THE_FOUR_KANGAROOS"></a><a href="#X_337_THE_FOUR_KANGAROOSa"><b>337.—THE FOUR KANGAROOS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q337.png" width="400" height="392" alt="" title="" /> +</div> + +<p>In introducing a little Commonwealth problem, I must first explain +that the diagram represents the sixty-four fields, all properly fenced +off from one another, of an Australian settlement, though I need +hardly say that our kith and kin "down under" always <i>do</i> set out +their land in this methodical and exact manner. It will be seen that +in every one of the four corners is a kangaroo. Why kangaroos have a +marked preference for corner plots has never been satisfactorily +explained, and it would be out of place to discuss the point here. I +should also add that kangaroos, as is well known, always leap in what +we call "knight's moves." In fact, chess players would probably have +adopted the better term "kangaroo's move" had not chess been invented +before kangaroos.</p> + +<p>The puzzle is simply this. One morning each kangaroo went for his +morning hop, and in sixteen consecutive knight's leaps visited just +fifteen different fields and jumped back to his corner. No field was +visited by more than one of the kangaroos. The diagram shows how they +arranged matters. What you are asked to do is to show how they might +have performed the feat without any kangaroo ever crossing the +horizontal line in the middle of the square that divides the board +into two equal parts.</p> + +<hr style="width: 30%;" /> +<p><a name="X_338_THE_BOARD_IN_COMPARTMENTS" id="X_338_THE_BOARD_IN_COMPARTMENTS"></a><a href="#X_338_THE_BOARD_IN_COMPARTMENTSa"><b>338.—THE BOARD IN COMPARTMENTS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q338.png" width="400" height="393" alt="" title="" /> +</div> + +<p>We cannot divide the ordinary chessboard into four equal square +compartments, and describe a complete tour, or even path, in each +compartment. But we may divide it into four compartments, as in the +illustration, two containing each twenty squares, and the other two +each twelve squares, and so obtain an interesting puzzle. You are +asked to describe a complete re-entrant tour on this board, starting +where you like, but visiting every square in each successive +compartment before passing into another one, and making the final leap +back to the square from which the knight set out. It is not difficult, +but will be found very entertaining and not uninstructive.</p> + +<p>Whether a re-entrant "tour" or a complete knight's "path" is possible +or not on a rectangular board of given dimensions depends not only on +its dimensions, but also on its shape. A tour is obviously not +possible on a board containing an odd number of cells, such as 5 by 5 +or 7 by 7, for this reason: Every successive leap of the knight must +be from a white square to a black and a black to a white alternately. +But if there be an odd number of cells or squares there must be one +more square of one colour than of the other, therefore the path must +begin from a square of the colour that is in excess, and end on a +similar colour, and as a knight's <span class='pagenum'>Pg 103<a name="Page_103" id="Page_103"></a></span>move from one colour to a similar +colour is impossible the path cannot be re-entrant. But a perfect tour +may be made on a rectangular board of any dimensions provided the +number of squares be even, and that the number of squares on one side +be not less than 6 and on the other not less than 5. In other words, +the smallest rectangular board on which a re-entrant tour is possible +is one that is 6 by 5.</p> + +<p>A complete knight's path (not re-entrant) over all the squares of a +board is never possible if there be only two squares on one side; nor +is it possible on a square board of smaller dimensions than 5 by 5. So +that on a board 4 by 4 we can neither describe a knight's tour nor a +complete knight's path; we must leave one square unvisited. Yet on a +board 4 by 3 (containing four squares fewer) a complete path may be +described in sixteen different ways. It may interest the reader to +discover all these. Every path that starts from and ends at different +squares is here counted as a different solution, and even reverse +routes are called different.</p> + +<hr style="width: 30%;" /> +<p><a name="X_339_THE_FOUR_KNIGHTS_TOURS" id="X_339_THE_FOUR_KNIGHTS_TOURS"></a><a href="#X_339_THE_FOUR_KNIGHTS_TOURSa"><b>339.—THE FOUR KNIGHTS' TOURS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q339.png" width="400" height="397" alt="" title="" /> +</div> + +<p>I will repeat that if a chessboard be cut into four equal parts, as +indicated by the dark lines in the illustration, it is not possible to +perform a knight's tour, either re-entrant or not, on one of the +parts. The best re-entrant attempt is shown, in which each knight has +to trespass twice on other parts. The puzzle is to cut the board +differently into four parts, each of the same size and shape, so that +a re-entrant knight's tour may be made on each part. Cuts along the +dotted lines will not do, as the four central squares of the board +would be either detached or hanging on by a mere thread.</p> + +<hr style="width: 30%;" /> +<p><a name="X_340_THE_CUBIC_KNIGHTS_TOUR" id="X_340_THE_CUBIC_KNIGHTS_TOUR"></a><a href="#X_340_THE_CUBIC_KNIGHTS_TOURa"><b>340.—THE CUBIC KNIGHT'S TOUR.</b></a></p> + +<p>Some few years ago I happened to read somewhere that Abnit +Vandermonde, a clever mathematician, who was born in 1736 and died in +1793, had devoted a good deal of study to the question of knight's +tours. Beyond what may be gathered from a few fragmentary references, +I am not aware of the exact nature or results of his investigations, +but one thing attracted my attention, and that was the statement that +he had proposed the question of a tour of the knight over the six +surfaces of a cube, each surface being a chessboard. Whether he +obtained a solution or not I do not know, but I have never seen one +published. So I at once set to work to master this interesting +problem. Perhaps the reader may like to attempt it.</p> + +<hr style="width: 30%;" /> +<p><a name="X_341_THE_FOUR_FROGS" id="X_341_THE_FOUR_FROGS"></a><a href="#X_341_THE_FOUR_FROGSa"><b>341.—THE FOUR FROGS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q341.png" width="400" height="397" alt="" title="" /> +</div> + +<p>In the illustration we have eight toadstools, with white frogs on 1 +and 3 and black frogs on 6 and 8. The puzzle is to move one frog at a +time, in any order, along one of the straight lines from toadstool to +toadstool, until they have exchanged places, the white frogs being +left on 6 and 8 and the black ones on 1 and 3. If you use four +counters on a simple diagram, you will find this quite easy, but it is +a little more puzzling to do it in only seven plays, any number of +successive moves by one frog counting as one play. Of course, more +than one frog cannot be on a toadstool at the same time.</p> + +<hr style="width: 30%;" /> +<p><a name="X_342_THE_MANDARINS_PUZZLE" id="X_342_THE_MANDARINS_PUZZLE"></a><a href="#X_342_THE_MANDARINS_PUZZLEa"><b>342.—THE MANDARIN'S PUZZLE.</b></a></p> + +<p>The following puzzle has an added interest from the circumstance that +a correct solution of it secured for a certain young Chinaman the hand +of his charming bride. The wealthiest mandarin within a radius of a +hundred miles of Peking was Hi-Chum-Chop, and his beautiful daughter, +Peeky-Bo, had innumerable admirers. One of her most ardent lovers was +Winky-Hi, and when he asked the old mandarin for his consent to their +marriage, Hi-Chum-Chop presented him with the following puzzle and +promised his consent if the youth brought him the correct answer +within a week. Winky-Hi, following a habit which obtains among certain +<span class='pagenum'>Pg 104<a name="Page_104" id="Page_104"></a></span>solvers to this day, gave it to all his friends, and when he had +compared their solutions he handed in the best one as his own. Luckily +it was quite right. The mandarin thereupon fulfilled his promise. The +fatted pup was killed for the wedding feast, and when Hi-Chum-Chop +passed Winky-Hi the liver wing all present knew that it was a token of +eternal goodwill, in accordance with Chinese custom from time +immemorial.</p> + +<p>The mandarin had a table divided into twenty-five squares, as shown in +the diagram. On each of twenty-four of these squares was placed a +numbered counter, just as I have indicated. The puzzle is to get the +counters in numerical order by moving them one at a time in what we +call "knight's moves." Counter 1 should be where 16 is, 2 where 11 is, +4 where 13 now is, and so on. It will be seen that all the counters on +shaded squares are in their proper positions. Of course, two counters +may never be on a square at the same time. Can you perform the feat in +the fewest possible moves?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q342.png" width="400" height="411" alt="" title="" /> +</div> + +<p>In order to make the manner of moving perfectly clear I will point out +that the first knight's move can only be made by 1 or by 2 or by 10. +Supposing 1 moves, then the next move must be by 23, 4, 8, or 21. As +there is never more than one square vacant, the order in which the +counters move may be written out as follows: 1—21—14—18—22, etc. A +rough diagram should be made on a larger scale for practice, and +numbered counters or pieces of cardboard used.</p> + +<hr style="width: 30%;" /> +<p><a name="X_343_EXERCISE_FOR_PRISONERS" id="X_343_EXERCISE_FOR_PRISONERS"></a><a href="#X_343_EXERCISE_FOR_PRISONERSa"><b>343.—EXERCISE FOR PRISONERS.</b></a></p> + +<p>The following is the plan of the north wing of a certain gaol, showing +the sixteen cells all communicating by open doorways. Fifteen +prisoners were numbered and arranged in the cells as shown. They were +allowed to change their cells as much as they liked, but if two +prisoners were ever in the same cell together there was a severe +punishment promised them.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q343.png" width="400" height="412" alt="" title="" /> +</div> + +<p>Now, in order to reduce their growing obesity, and to combine physical +exercise with mental recreation, the prisoners decided, on the +suggestion of one of their number who was interested in knight's +tours, to try to form themselves into a perfect knight's path without +breaking the prison regulations, and leaving the bottom right-hand +corner cell vacant, as originally. The joke of the matter is that the +arrangement at which they arrived was as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>8</td><td align='right'>3</td><td align='right'>12</td><td align='right'>1</td></tr> +<tr><td align='right'>11</td><td align='right'>14</td><td align='right'>9</td><td align='right'>6</td></tr> +<tr><td align='right'>4</td><td align='right'>7</td><td align='right'>2</td><td align='right'>13</td></tr> +<tr><td align='right'>15</td><td align='right'>10</td><td align='right'>5</td></tr> +</table></div> + +<p>The warders failed to detect the important fact that the men could not +possibly get into this position without two of them having been at +some time in the same cell together. Make the attempt with counters on +a ruled diagram, and you will find that this is so. Otherwise the +solution is correct enough, each member being, as required, a knight's +move from the preceding number, and the original corner cell vacant.</p> + +<p>The puzzle is to start with the men placed as in the illustration and +show how it might have been done in the fewest moves, while giving a +complete rest to as many prisoners as possible.</p> + +<p>As there is never more than one vacant cell for a man to enter, it is +only necessary to write down the numbers of the men in the order in +which they move. It is clear that very few men can be left throughout +in their cells undisturbed, but I will leave the solver to discover +just how many, as this is a very essential part of the puzzle.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 105<a name="Page_105" id="Page_105"></a></span><a name="X_344_THE_KENNEL_PUZZLE" id="X_344_THE_KENNEL_PUZZLE"></a><a href="#X_344_THE_KENNEL_PUZZLEa"><b>344.—THE KENNEL PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q344.png" width="400" height="397" alt="" title="" /> +</div> + +<p>A man has twenty-five dog kennels all communicating with each other by +doorways, as shown in the illustration. He wishes to arrange his +twenty dogs so that they shall form a knight's string from dog No. 1 +to dog No. 20, the bottom row of five kennels to be left empty, as at +present. This is to be done by moving one dog at a time into a vacant +kennel. The dogs are well trained to obedience, and may be trusted to +remain in the kennels in which they are placed, except that if two are +placed in the same kennel together they will fight it out to the +death. How is the puzzle to be solved in the fewest possible moves +without two dogs ever being together?</p> + +<hr style="width: 30%;" /> +<p><a name="X_345_THE_TWO_PAWNS" id="X_345_THE_TWO_PAWNS"></a><a href="#X_345_THE_TWO_PAWNSa"><b>345.—THE TWO PAWNS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q345.png" width="400" height="428" alt="" title="" /> +</div> + +<p>Here is a neat little puzzle in counting. In how many different ways +may the two pawns advance to the eighth square? You may move them in +any order you like to form a different sequence. For example, you may +move the Q R P (one or two squares) first, or the K R P first, or one +pawn as far as you like before touching the other. Any sequence is +permissible, only in this puzzle as soon as a pawn reaches the eighth +square it is dead, and remains there unconverted. Can you count the +number of different sequences? At first it will strike you as being +very difficult, but I will show that it is really quite simple when +properly attacked.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="VARIOUS_CHESS_PUZZLES" id="VARIOUS_CHESS_PUZZLES"></a><a href="#CONTENTS">VARIOUS CHESS PUZZLES.</a></h2> + +<p class='center'> +"Chesse-play is a good and wittie exercise of +the minde for some kinde of men."<br /> +<span style="margin-left: 8em;">Burton's <i>Anatomy of Melancholy</i>.<br /></span> +</p> + +<hr style="width: 30%;" /> +<p><a name="X_346_SETTING_THE_BOARD" id="X_346_SETTING_THE_BOARD"></a><a href="#X_346_SETTING_THE_BOARDa"><b>346.—SETTING THE BOARD.</b></a></p> + +<p>I have a single chessboard and a single set of chessmen. In how many +different ways may the men be correctly set up for the beginning of a +game? I find that most people slip at a particular point in making the +calculation.</p> + +<hr style="width: 30%;" /> +<p><a name="X_347_COUNTING_THE_RECTANGLES" id="X_347_COUNTING_THE_RECTANGLES"></a><a href="#X_347_COUNTING_THE_RECTANGLESa"><b>347.—COUNTING THE RECTANGLES.</b></a></p> + +<p>Can you say correctly just how many squares and other rectangles the +chessboard contains? In other words, in how great a number of +different ways is it possible to indicate a square or other rectangle +enclosed by lines that separate the squares of the board?</p> + +<hr style="width: 30%;" /> +<p><a name="X_348_THE_ROOKERY" id="X_348_THE_ROOKERY"></a><a href="#X_348_THE_ROOKERYa"><b>348.—THE ROOKERY.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q348.png" width="400" height="400" alt="" title="" /> +</div> + +<p>The White rooks cannot move outside the little square in which they +are enclosed except on the final move, in giving checkmate. The puzzle +<span class='pagenum'>Pg 106<a name="Page_106" id="Page_106"></a></span>is how to checkmate Black in the fewest possible moves with No. 8 +rook, the other rooks being left in numerical order round the sides of +their square with the break between 1 and 7.</p> + +<hr style="width: 30%;" /> +<p><a name="X_349_STALEMATE" id="X_349_STALEMATE"></a><a href="#X_349_STALEMATEa"><b>349.—STALEMATE.</b></a></p> + +<p>Some years ago the puzzle was proposed to construct an imaginary game +of chess, in which White shall be stalemated in the fewest possible +moves with all the thirty-two pieces on the board. Can you build up +such a position in fewer than twenty moves?</p> + +<hr style="width: 30%;" /> +<p><a name="X_350_THE_FORSAKEN_KING" id="X_350_THE_FORSAKEN_KING"></a><a href="#X_350_THE_FORSAKEN_KINGa"><b>350.—THE FORSAKEN KING.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q350.png" width="400" height="400" alt="" title="" /> +</div> + +<p>Set up the position shown in the diagram. Then the condition of the +puzzle is—White to play and checkmate in six moves. Notwithstanding +the complexities, I will show how the manner of play may be condensed +into quite a few lines, merely stating here that the first two moves +of White cannot be varied.</p> + +<hr style="width: 30%;" /> +<p><a name="X_351_THE_CRUSADER" id="X_351_THE_CRUSADER"></a><a href="#X_351_THE_CRUSADERa"><b>351.—THE CRUSADER.</b></a></p> + +<p>The following is a prize puzzle propounded by me some years ago. +Produce a game of chess which, after sixteen moves, shall leave White +with all his sixteen men on their original squares and Black in +possession of his king alone (not necessarily on his own square). +White is then to <i>force</i> mate in three moves.</p> + +<hr style="width: 30%;" /> +<p><a name="X_352_IMMOVABLE_PAWNS" id="X_352_IMMOVABLE_PAWNS"></a><a href="#X_352_IMMOVABLE_PAWNSa"><b>352.—IMMOVABLE PAWNS.</b></a></p> + +<p>Starting from the ordinary arrangement of the pieces as for a game, +what is the smallest possible number of moves necessary in order to +arrive at the following position? The moves for both sides must, of +course, be played strictly in accordance with the rules of the game, +though the result will necessarily be a very weird kind of chess.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q352.png" width="400" height="430" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_353_THIRTY-SIX_MATES" id="X_353_THIRTY-SIX_MATES"></a><a href="#X_353_THIRTY-SIX_MATESa"><b>353.—THIRTY-SIX MATES.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q353.png" width="400" height="400" alt="" title="" /> +</div> + +<p>Place the remaining eight White pieces in such a position that White +shall have the choice of thirty-six different mates on the move. Every +move that checkmates and leaves a different position is a different +mate. The pieces already placed must not be moved.</p> + +<hr style="width: 30%;" /> +<p><a name="X_354_AN_AMAZING_DILEMMA" id="X_354_AN_AMAZING_DILEMMA"></a><a href="#X_354_AN_AMAZING_DILEMMAa"><b>354.—AN AMAZING DILEMMA.</b></a></p> + +<p>In a game of chess between Mr. Black and Mr. White, Black was in +difficulties, and as usual was obliged to catch a train. So he +proposed that White should complete the game in his absence on +condition that no moves whatever <span class='pagenum'>Pg 107<a name="Page_107" id="Page_107"></a></span>should be made for Black, but only +with the White pieces. Mr. White accepted, but to his dismay found it +utterly impossible to win the game under such conditions. Try as he +would, he could not checkmate his opponent. On which square did Mr. +Black leave his king? The other pieces are in their proper positions +in the diagram. White may leave Black in check as often as he likes, +for it makes no difference, as he can never arrive at a checkmate +position.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q354.png" width="400" height="434" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_355_CHECKMATE" id="X_355_CHECKMATE"></a><a href="#X_355_CHECKMATEa"><b>355.—CHECKMATE!</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q355.png" width="400" height="430" alt="" title="" /> +</div> + +<p>Strolling into one of the rooms of a London club, I noticed a position +left by two players who had gone. This position is shown in the +diagram. It is evident that White has checkmated Black. But how did he +do it? That is the puzzle.</p> + +<hr style="width: 30%;" /> +<p><a name="X_356_QUEER_CHESS" id="X_356_QUEER_CHESS"></a><a href="#X_356_QUEER_CHESSa"><b>356.—QUEER CHESS.</b></a></p> + +<p>Can you place two White rooks and a White knight on the board so that +the Black king (who must be on one of the four squares in the middle +of the board) shall be in check with no possible move open to him? "In +other words," the reader will say, "the king is to be shown +checkmated." Well, you can use the term if you wish, though I +intentionally do not employ it myself. The mere fact that there is no +White king on the board would be a sufficient reason for my not doing +so.</p> + +<hr style="width: 30%;" /> +<p><a name="X_357_ANCIENT_CHINESE_PUZZLE" id="X_357_ANCIENT_CHINESE_PUZZLE"></a><a href="#X_357_ANCIENT_CHINESE_PUZZLEa"><b>357.—ANCIENT CHINESE PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q357.png" width="400" height="449" alt="" title="" /> +</div> + +<p>My next puzzle is supposed to be Chinese, many hundreds of years old, +and never fails to interest. White to play and mate, moving each of +the three pieces once, and once only.</p> + +<hr style="width: 30%;" /> +<p><a name="X_358_THE_SIX_PAWNS" id="X_358_THE_SIX_PAWNS"></a><a href="#X_358_THE_SIX_PAWNSa"><b>358.—THE SIX PAWNS.</b></a></p> + +<p>In how many different ways may I place six pawns on the chessboard so +that there shall be an even number of unoccupied squares in every row +and every column? We are not here considering the diagonals at all, +and every different six squares occupied makes a different solution, +so we have not to exclude reversals or reflections.</p> + +<hr style="width: 30%;" /> +<p><a name="X_359_COUNTER_SOLITAIRE" id="X_359_COUNTER_SOLITAIRE"></a><a href="#X_359_COUNTER_SOLITAIREa"><b>359.—COUNTER SOLITAIRE.</b></a></p> + +<p>Here is a little game of solitaire that is quite easy, but not so easy +as to be uninteresting. You can either rule out the squares on a sheet +of cardboard or paper, or you can use a portion <span class='pagenum'>Pg 108<a name="Page_108" id="Page_108"></a></span>of your chessboard. I +have shown numbered counters in the illustration so as to make the +solution easy and intelligible to all, but chess pawns or draughts +will serve just as well in practice.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q359.png" width="400" height="156" alt="" title="" /> +</div> + +<p>The puzzle is to remove all the counters except one, and this one that +is left must be No. 1. You remove a counter by jumping over another +counter to the next space beyond, if that square is vacant, but you +cannot make a leap in a diagonal direction. The following moves will +make the play quite clear: 1-9, 2-10, 1-2, and so on. Here 1 jumps +over 9, and you remove 9 from the board; then 2 jumps over 10, and you +remove 10; then 1 jumps over 2, and you remove 2. Every move is thus a +capture, until the last capture of all is made by No. 1.</p> + +<hr style="width: 30%;" /> +<p><a name="X_360_CHESSBOARD_SOLITAIRE" id="X_360_CHESSBOARD_SOLITAIRE"></a><a href="#X_360_CHESSBOARD_SOLITAIREa"><b>360.—CHESSBOARD SOLITAIRE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q360.png" width="400" height="397" alt="" title="" /> +</div> + +<p>Here is an extension of the last game of solitaire. All you need is a +chessboard and the thirty-two pieces, or the same number of draughts +or counters. In the illustration numbered counters are used. The +puzzle is to remove all the counters except two, and these two must +have originally been on the same side of the board; that is, the two +left must either belong to the group 1 to 16 or to the other group, 17 +to 32. You remove a counter by jumping over it with another counter to +the next square beyond, if that square is vacant, but you cannot make +a leap in a diagonal direction. The following moves will make the play +quite clear: 3-11, 4-12, 3-4, 13-3. Here 3 jumps over 11, and you +remove 11; 4 jumps over 12, and you remove 12; and so on. It will be +found a fascinating little game of patience, and the solution requires +the exercise of some ingenuity.</p> + +<hr style="width: 30%;" /> +<p><a name="X_361_THE_MONSTROSITY" id="X_361_THE_MONSTROSITY"></a><a href="#X_361_THE_MONSTROSITYa"><b>361.—THE MONSTROSITY.</b></a></p> + +<p>One Christmas Eve I was travelling by rail to a little place in one of +the southern counties. The compartment was very full, and the +passengers were wedged in very tightly. My neighbour in one of the +corner seats was closely studying a position set up on one of those +little folding chessboards that can be carried conveniently in the +pocket, and I could scarcely avoid looking at it myself. Here is the +position:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q361.png" width="400" height="445" alt="" title="" /> +</div> + +<p>My fellow-passenger suddenly turned his head and caught the look of +bewilderment on my face.</p> + +<p>"Do you play chess?" he asked.</p> + +<p>"Yes, a little. What is that? A problem?"</p> + +<p>"Problem? No; a game."</p> + +<p>"Impossible!" I exclaimed rather rudely. "The position is a perfect +monstrosity!"</p> + +<p>He took from his pocket a postcard and handed it to me. It bore an +address at one side and on the other the words "43. K to Kt 8."</p> + +<p>"It is a correspondence game." he exclaimed. "That is my friend's last +move, and I am considering my reply."</p> + +<p>"But you really must excuse me; the position seems utterly impossible. +How on earth, for example—"</p> + +<p>"Ah!" he broke in smilingly. "I see; you are a beginner; you play to +win."</p> + +<p><span class='pagenum'>Pg 109<a name="Page_109" id="Page_109"></a></span>"Of course you wouldn't play to lose or draw!"</p> + +<p>He laughed aloud.</p> + +<p>"You have much to learn. My friend and myself do not play for results +of that antiquated kind. We seek in chess the wonderful, the +whimsical, the weird. Did you ever see a position like that?"</p> + +<p>I inwardly congratulated myself that I never had.</p> + +<p>"That position, sir, materializes the sinuous evolvements and +syncretic, synthetic, and synchronous concatenations of two cerebral +individualities. It is the product of an amphoteric and intercalatory +interchange of—"</p> + +<p>"Have you seen the evening paper, sir?" interrupted the man opposite, +holding out a newspaper. I noticed on the margin beside his thumb some +pencilled writing. Thanking him, I took the paper and read—"Insane, +but quite harmless. He is in my charge."</p> + +<p>After that I let the poor fellow run on in his wild way until both got +out at the next station.</p> + +<p>But that queer position became fixed indelibly in my mind, with +Black's last move 43. K to Kt 8; and a short time afterwards I found +it actually possible to arrive at such a position in forty-three +moves. Can the reader construct such a sequence? How did White get his +rooks and king's bishop into their present positions, considering +Black can never have moved his king's bishop? No odds were given, and +every move was perfectly legitimate.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="MEASURING_WEIGHING_AND_PACKING_PUZZLES" id="MEASURING_WEIGHING_AND_PACKING_PUZZLES"></a><a href="#CONTENTS">MEASURING, WEIGHING, AND PACKING PUZZLES.</a></h2> + +<p class='center'> +"Measure still for measure."<br /> +<span style="margin-left: 8em;"><i>Measure for Measure</i>, v. 1.</span><br /> +</p> + + +<p>Apparently the first printed puzzle involving the measuring of a given +quantity of liquid by pouring from one vessel to others of known +capacity was that propounded by Niccola Fontana, better known as +"Tartaglia" (the stammerer), 1500-1559. It consists in dividing 24 oz. +of valuable balsam into three equal parts, the only measures available +being vessels holding 5, 11, and 13 ounces respectively. There are +many different solutions to this puzzle in six manipulations, or +pourings from one vessel to another. Bachet de Méziriac reprinted this +and other of Tartaglia's puzzles in his <i>Problèmes plaisans et +délectables</i> (1612). It is the general opinion that puzzles of this +class can only be solved by trial, but I think formulæ can be +constructed for the solution generally of certain related cases. It is +a practically unexplored field for investigation.</p> + +<p>The classic weighing problem is, of course, that proposed by Bachet. +It entails the determination of the least number of weights that would +serve to weigh any integral number of pounds from 1 lb. to 40 lbs. +inclusive, when we are allowed to put a weight in either of the two +pans. The answer is 1, 3, 9, and 27 lbs. Tartaglia had previously +propounded the same puzzle with the condition that the weights may +only be placed in one pan. The answer in that case is 1, 2, 4, 8, 16, +32 lbs. Major MacMahon has solved the problem quite generally. A full +account will be found in Ball's <i>Mathematical Recreations</i> (5th +edition).</p> + +<p>Packing puzzles, in which we are required to pack a maximum number of +articles of given dimensions into a box of known dimensions, are, I +believe, of quite recent introduction. At least I cannot recall any +example in the books of the old writers. One would rather expect to +find in the toy shops the idea presented as a mechanical puzzle, but I +do not think I have ever seen such a thing. The nearest approach to it +would appear to be the puzzles of the jig-saw character, where there +is only one depth of the pieces to be adjusted.</p> + +<hr style="width: 30%;" /> +<p><a name="X_362_THE_WASSAIL_BOWL" id="X_362_THE_WASSAIL_BOWL"></a><a href="#X_362_THE_WASSAIL_BOWLa"><b>362.—THE WASSAIL BOWL.</b></a></p> + +<p>One Christmas Eve three Weary Willies came into possession of what was +to them a veritable wassail bowl, in the form of a small barrel, +containing exactly six quarts of fine ale. One of the men possessed a +five-pint jug and another a three-pint jug, and the problem for them +was to divide the liquor equally amongst them without waste. Of +course, they are not to use any other vessels or measures. If you can +show how it was to be done at all, then try to find the way that +requires the fewest possible manipulations, every separate pouring +from one vessel to another, or down a man's throat, counting as a +manipulation.</p> + +<hr style="width: 30%;" /> +<p><a name="X_363_THE_DOCTORS_QUERY" id="X_363_THE_DOCTORS_QUERY"></a><a href="#X_363_THE_DOCTORS_QUERYa"><b>363.—THE DOCTOR'S QUERY.</b></a></p> + +<p>"A curious little point occurred to me in my dispensary this morning," +said a doctor. "I had a bottle containing ten ounces of spirits of +wine, and another bottle containing ten ounces of water. I poured a +quarter of an ounce of spirits into the water and shook them up +together. The mixture was then clearly forty to one. Then I poured +back a quarter-ounce of the mixture, so that the two bottles should +again each contain the same quantity of fluid. What proportion of +spirits to water did the spirits of wine bottle then contain?"</p> + +<hr style="width: 30%;" /> +<p><a name="X_364_THE_BARREL_PUZZLE" id="X_364_THE_BARREL_PUZZLE"></a><a href="#X_364_THE_BARREL_PUZZLEa"><b>364.—THE BARREL PUZZLE.</b></a></p> + +<p>The men in the illustration are disputing over the liquid contents of +a barrel. What the particular liquid is it is impossible to say, for +we are unable to look into the barrel; so we will call it water. One +man says that the barrel is more than half full, while the other +insists that it is not half full. What is their easiest way of +settling the point? It is not necessary to use stick, string, or +implement of any kind for measuring. I <span class='pagenum'>Pg 110<a name="Page_110" id="Page_110"></a></span>give this merely as one of the +simplest possible examples of the value of ordinary sagacity in the +solving of puzzles. What are apparently very difficult problems may +frequently be solved in a similarly easy manner if we only use a +little common sense.</p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/q364.png" width="500" height="451" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_365_NEW_MEASURING_PUZZLE" id="X_365_NEW_MEASURING_PUZZLE"></a><a href="#X_365_NEW_MEASURING_PUZZLEa"><b>365.—NEW MEASURING PUZZLE.</b></a></p> + +<p>Here is a new poser in measuring liquids that will be found +interesting. A man has two ten-quart vessels full of wine, and a +five-quart and a four-quart measure. He wants to put exactly three +quarts into each of the two measures. How is he to do it? And how many +manipulations (pourings from one vessel to another) do you require? Of +course, waste of wine, tilting, and other tricks are not allowed.</p> + +<hr style="width: 30%;" /> +<p><a name="X_366_THE_HONEST_DAIRYMAN" id="X_366_THE_HONEST_DAIRYMAN"></a><a href="#X_366_THE_HONEST_DAIRYMANa"><b>366.—THE HONEST DAIRYMAN.</b></a></p> + +<p>An honest dairyman in preparing his milk for public consumption +employed a can marked B, containing milk, and a can marked A, +containing water. From can A he poured enough to double the contents +of can B. Then he poured from can B into can A enough to double its +contents. Then he finally poured from can A into can B until their +contents were exactly equal. After these operations he would send the +can A to London, and the puzzle is to discover what are the relative +proportions of milk and water that he provides for the Londoners' +breakfast-tables. Do they get equal proportions of milk and water—or +two parts of milk and one of water—or what? It is an interesting +question, though, curiously enough, we are not told how much milk or +water he puts into the cans at the start of his operations.</p> + +<hr style="width: 30%;" /> +<p><a name="X_367_WINE_AND_WATER" id="X_367_WINE_AND_WATER"></a><a href="#X_367_WINE_AND_WATERa"><b>367.—WINE AND WATER.</b></a></p> + +<p>Mr. Goodfellow has adopted a capital idea of late. When he gives a +little dinner party and the time arrives to smoke, after the departure +of the ladies, he sometimes finds that the conversation is apt to +become too political, too personal, too slow, or too scandalous. Then +he always manages to introduce to the company some new poser that he +has secreted up his sleeve for the occasion. This invariably results +in no end of interesting discussion and debate, and puts everybody in +a good humour.</p> + +<p>Here is a little puzzle that he propounded the other night, and it is +extraordinary how the company differed in their answers. He filled a +wine-glass half full of wine, and another glass twice the size +one-third full of wine. Then he filled up each glass with water and +emptied the contents of both into a tumbler. "Now," he said, "what +part of the mixture is wine and what part water?" Can you give the +correct answer?</p> + +<hr style="width: 30%;" /> +<p><a name="X_368_THE_KEG_OF_WINE" id="X_368_THE_KEG_OF_WINE"></a><a href="#X_368_THE_KEG_OF_WINEa"><b>368.—THE KEG OF WINE.</b></a></p> + +<p>Here is a curious little problem. A man had a ten-gallon keg full of +wine and a jug. One day he drew off a jugful of wine and filled up the +keg with water. Later on, when the wine and water had got thoroughly +mixed, he drew off <span class='pagenum'>Pg 111<a name="Page_111" id="Page_111"></a></span>another jugful and again filled up the keg with +water. It was then found that the keg contained equal proportions of +wine and water. Can you find from these facts the capacity of the jug?</p> + +<hr style="width: 30%;" /> +<p><a name="X_369_MIXING_THE_TEA" id="X_369_MIXING_THE_TEA"></a><a href="#X_369_MIXING_THE_TEAa"><b>369.—MIXING THE TEA.</b></a></p> + +<p>"Mrs. Spooner called this morning," said the honest grocer to his +assistant. "She wants twenty pounds of tea at 2<i>s</i>. 4½<i>d</i>. per lb. Of +course we have a good 2<i>s</i>. 6<i>d</i>. tea, a slightly inferior at 2<i>s</i>. 3<i>d</i>., and +a cheap Indian at 1<i>s</i>. 9<i>d</i>., but she is very particular always about her +prices."</p> + +<p>"What do you propose to do?" asked the innocent assistant.</p> + +<p>"Do?" exclaimed the grocer. "Why, just mix up the three teas in +different proportions so that the twenty pounds will work out fairly +at the lady's price. Only don't put in more of the best tea than you +can help, as we make less profit on that, and of course you will use +only our complete pound packets. Don't do any weighing."</p> + +<p>How was the poor fellow to mix the three teas? Could you have shown +him how to do it?</p> + +<hr style="width: 30%;" /> +<p><a name="X_370_A_PACKING_PUZZLE" id="X_370_A_PACKING_PUZZLE"></a><a href="#X_370_A_PACKING_PUZZLEa"><b>370.—A PACKING PUZZLE.</b></a></p> + +<p>As we all know by experience, considerable ingenuity is often +required in packing articles into a box if space is not to be unduly +wasted. A man once told me that he had a large number of iron balls, all +exactly two inches in diameter, and he wished to pack as many of these +as possible into a rectangular box 24<sup>9</sup>/<sub>10</sub> inches long, 22<sup>4</sup>/<sub>5</sub> inches +wide, and 14 inches deep. Now, what is the greatest number of the balls +that he could pack into that box?</p> + +<hr style="width: 30%;" /> +<p><a name="X_371_GOLD_PACKING_IN_RUSSIA" id="X_371_GOLD_PACKING_IN_RUSSIA"></a><a href="#X_371_GOLD_PACKING_IN_RUSSIAa"><b>371.—GOLD PACKING IN RUSSIA.</b></a></p> + +<p>The editor of the <i>Times</i> newspaper was invited by a high Russian +official to inspect the gold stored in reserve at St. Petersburg, in +order that he might satisfy himself that it was not another "Humbert +safe." He replied that it would be of no use whatever, for although +the gold might appear to be there, he would be quite unable from a +mere inspection to declare that what he saw was really gold. A +correspondent of the <i>Daily Mail</i> thereupon took up the challenge, +but, although he was greatly impressed by what he saw, he was +compelled to confess his incompetence (without emptying and counting +the contents of every box and sack, and assaying every piece of gold) +to give any assurance on the subject. In presenting the following +little puzzle, I wish it to be also understood that I do not guarantee +the real existence of the gold, and the point is not at all material +to our purpose. Moreover, if the reader says that gold is not usually +"put up" in slabs of the dimensions that I give, I can only claim +problematic licence.</p> + +<p>Russian officials were engaged in packing 800 gold slabs, each +measuring 12½ inches long, 11 inches wide, and 1 inch deep. What +are the interior dimensions of a box of equal length and width, and +necessary depth, that will exactly contain them without any space +being left over? Not more than twelve slabs may be laid on edge, +according to the rules of the government. It is an interesting little +problem in packing, and not at all difficult.</p> + +<hr style="width: 30%;" /> +<p><a name="X_372_THE_BARRELS_OF_HONEY" id="X_372_THE_BARRELS_OF_HONEY"></a><a href="#X_372_THE_BARRELS_OF_HONEYa"><b>372.—THE BARRELS OF HONEY.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q372.png" width="400" height="332" alt="" title="" /> +</div> + +<p>Once upon a time there was an aged merchant of Bagdad who was much +respected by all who knew him. He had three sons, and it was a rule of +his life to treat them all exactly alike. Whenever one received a +present, the other two were each given one of equal value. One day +this worthy man fell sick and died, bequeathing all his possessions to +his three sons in equal shares.</p> + +<p>The only difficulty that arose was over the stock of honey. There were +exactly twenty-one barrels. The old man had left instructions that not +only should every son receive an equal quantity of honey, but should +receive exactly the same number of barrels, and that no honey should +be transferred from barrel to barrel on account of the waste involved. +Now, as seven of these barrels were full of honey, seven were +half-full, and seven were empty, this was found to be quite a puzzle, +especially as each brother objected to taking more than four barrels +of, the same description—full, half-full, or empty. Can you show how +they succeeded in making a correct division of the property?</p> + + + +<hr style="width: 65%;" /><p><span class='pagenum'>Pg 112<a name="Page_112" id="Page_112"></a></span></p> +<h2><a name="CROSSING_RIVER_PROBLEMS" id="CROSSING_RIVER_PROBLEMS"></a><a href="#CONTENTS">CROSSING RIVER PROBLEMS</a></h2> + +<p class='center'> +"My boat is on the shore."<br /> +<span style="margin-left: 8em;">BYRON.</span><br /> +</p> + + +<p>This is another mediæval class of puzzles. Probably the earliest +example was by Abbot Alcuin, who was born in Yorkshire in 735 and died +at Tours in 804. And everybody knows the story of the man with the +wolf, goat, and basket of cabbages whose boat would only take one of +the three at a time with the man himself. His difficulties arose from +his being unable to leave the wolf alone with the goat, or the goat +alone with the cabbages. These puzzles were considered by Tartaglia +and Bachet, and have been later investigated by Lucas, De Fonteney, +Delannoy, Tarry, and others. In the puzzles I give there will be found +one or two new conditions which add to the complexity somewhat. I also +include a pulley problem that practically involves the same +principles.</p> + + +<hr style="width: 30%;" /> +<p><a name="X_373_CROSSING_THE_STREAM" id="X_373_CROSSING_THE_STREAM"></a><a href="#X_373_CROSSING_THE_STREAMa"><b>373.—CROSSING THE STREAM.</b></a></p> + +<p>During a country ramble Mr. and Mrs. Softleigh found themselves in a +pretty little dilemma. They had to cross a stream in a small boat +which was capable of carrying only 150 lbs. weight. But Mr. Softleigh +and his wife each weighed exactly 150 lbs., and each of their sons +weighed 75 lbs. And then there was the dog, who could not be induced +on any terms to swim. On the principle of "ladies first," they at once +sent Mrs. Softleigh over; but this was a stupid oversight, because she +had to come back again with the boat, so nothing was gained by that +operation. How did they all succeed in getting across? The reader will +find it much easier than the Softleigh family did, for their greatest +enemy could not have truthfully called them a brilliant +quartette—while the dog was a perfect fool.</p> + +<hr style="width: 30%;" /> +<p><a name="X_374_CROSSING_THE_RIVER_AXE" id="X_374_CROSSING_THE_RIVER_AXE"></a><a href="#X_374_CROSSING_THE_RIVER_AXEa"><b>374.—CROSSING THE RIVER AXE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q374.png" width="400" height="456" alt="" title="" /> +</div> + +<p>Many years ago, in the days of the smuggler known as "Rob Roy of the +West," a piratical band buried on the coast of South Devon a quantity +of treasure which was, of course, abandoned by them in the usual +inexplicable way. Some time afterwards its whereabouts was discovered +by three countrymen, who visited the spot one night and divided the +spoil between them, Giles taking treasure to the value of £800, Jasper +£500 worth, and Timothy £300 worth. In returning they had to cross the +river Axe at a point where they had left a small boat in readiness. +Here, however, was a difficulty they had not anticipated. The boat +would only carry two men, or one man and a sack, and they had so +little confidence in one another that no person could be left alone on +the land or in the boat with more than his share of the spoil, though +two persons (being a check on each other) might be left with more than +their shares. The puzzle is to show how they got over the river in the +fewest possible crossings, taking their treasure with them. No +<span class='pagenum'>Pg 113<a name="Page_113" id="Page_113"></a></span>tricks, such as ropes, "flying bridges," currents, swimming, or +similar dodges, may be employed.</p> + +<hr style="width: 30%;" /> +<p><a name="X_375_FIVE_JEALOUS_HUSBANDS" id="X_375_FIVE_JEALOUS_HUSBANDS"></a><a href="#X_375_FIVE_JEALOUS_HUSBANDSa"><b>375.—FIVE JEALOUS HUSBANDS.</b></a></p> + +<p>During certain local floods five married couples found themselves +surrounded by water, and had to escape from their unpleasant position +in a boat that would only hold three persons at a time. Every husband +was so jealous that he would not allow his wife to be in the boat or +on either bank with another man (or with other men) unless he was +himself present. Show the quickest way of getting these five men and +their wives across into safety.</p> + +<p>Call the men A, B, C, D, E, and their respective wives a, b, c, d, e. +To go over and return counts as two crossings. No tricks such as +ropes, swimming, currents, etc., are permitted.</p> + +<hr style="width: 30%;" /> +<p><a name="X_376_THE_FOUR_ELOPEMENTS" id="X_376_THE_FOUR_ELOPEMENTS"></a><a href="#X_376_THE_FOUR_ELOPEMENTSa"><b>376.—THE FOUR ELOPEMENTS.</b></a></p> + +<p>Colonel B—— was a widower of a very taciturn disposition. His +treatment of his four daughters was unusually severe, almost cruel, +and they not unnaturally felt disposed to resent it. Being charming +girls with every virtue and many accomplishments, it is not surprising +that each had a fond admirer. But the father forbade the young men to +call at his house, intercepted all letters, and placed his daughters +under stricter supervision than ever. But love, which scorns locks and +keys and garden walls, was equal to the occasion, and the four youths +conspired together and planned a general elopement.</p> + +<p>At the foot of the tennis lawn at the bottom of the garden ran the +silver Thames, and one night, after the four girls had been safely +conducted from a dormitory window to <i>terra firma</i>, they all crept +softly down to the bank of the river, where a small boat belonging to +the Colonel was moored. With this they proposed to cross to the +opposite side and make their way to a lane where conveyances were +waiting to carry them in their flight. Alas! here at the water's brink +their difficulties already began.</p> + +<p>The young men were so extremely jealous that not one of them would +allow his prospective bride to remain at any time in the company of +another man, or men, unless he himself were present also. Now, the +boat would only hold two persons, though it could, of course, be rowed +by one, and it seemed impossible that the four couples would ever get +across. But midway in the stream was a small island, and this seemed +to present a way out of the difficulty, because a person or persons +could be left there while the boat was rowed back or to the opposite +shore. If they had been prepared for their difficulty they could have +easily worked out a solution to the little poser at any other time. +But they were now so hurried and excited in their flight that the +confusion they soon got into was exceedingly amusing—or would have +been to any one except themselves.</p> + +<p>As a consequence they took twice as long and crossed the river twice +as often as was really necessary. Meanwhile, the Colonel, who was a +very light sleeper, thought he heard a splash of oars. He quickly +raised the alarm among his household, and the young ladies were found +to be missing. Somebody was sent to the police-station, and a number +of officers soon aided in the pursuit of the fugitives, who, in +consequence of that delay in crossing the river, were quickly +overtaken. The four girls returned sadly to their homes, and +afterwards broke off their engagements in disgust.</p> + +<p>For a considerable time it was a mystery how the party of eight +managed to cross the river in that little boat without any girl being +ever left with a man, unless her betrothed was also present. The +favourite method is to take eight counters or pieces of cardboard and +mark them A, B, C, D, a, b, c, d, to represent the four men and their +prospective brides, and carry them from one side of a table to the +other in a matchbox (to represent the boat), a penny being placed in +the middle of the table as the island.</p> + +<p>Readers are now asked to find the quickest method of getting the party +across the river. How many passages are necessary from land to land? +By "land" is understood either shore or island. Though the boat would +not necessarily call at the island every time of crossing, the +possibility of its doing so must be provided for. For example, it +would not do for a man to be alone in the boat (though it were +understood that he intended merely to cross from one bank to the +opposite one) if there happened to be a girl alone on the island other +than the one to whom he was engaged.</p> + +<hr style="width: 30%;" /> +<p><a name="X_377_STEALING_THE_CASTLE_TREASURE" id="X_377_STEALING_THE_CASTLE_TREASURE"></a><a href="#X_377_STEALING_THE_CASTLE_TREASUREa"><b>377.—STEALING THE CASTLE TREASURE.</b></a></p> + +<p>The ingenious manner in which a box of treasure, consisting +principally of jewels and precious stones, was stolen from Gloomhurst +Castle has been handed down as a tradition in the De Gourney family. +The thieves consisted of a man, a youth, and a small boy, whose only +mode of escape with the box of treasure was by means of a high window. +Outside the window was fixed a pulley, over which ran a rope with a +basket at each end. When one basket was on the ground the other was at +the window. The rope was so disposed that the persons in the basket +could neither help themselves by means of it nor receive help from +others. In short, the only way the baskets could be used was by +placing a heavier weight in one than in the other.</p> + +<p>Now, the man weighed 195 lbs., the youth 105 lbs., the boy 90 lbs., +and the box of treasure 75 lbs. The weight in the descending basket +could not exceed that in the other by more than 15 lbs. without +causing a descent so rapid as to be most dangerous to a human being, +though it would not injure the stolen property. Only two persons, or +one person and the treasure, could be placed in the same basket at one +time. How did they all manage to escape and take the box of treasure +with them?</p> + +<p><span class='pagenum'>Pg 114<a name="Page_114" id="Page_114"></a></span>The puzzle is to find the shortest way of performing the feat, which +in itself is not difficult. Remember, a person cannot help himself by +hanging on to the rope, the only way being to go down "with a bump," +with the weight in the other basket as a counterpoise.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="PROBLEMS_CONCERNING_GAMES" id="PROBLEMS_CONCERNING_GAMES"></a><a href="#CONTENTS">PROBLEMS CONCERNING GAMES.</a></h2> + +<p class='center'> +"The little pleasure of the game."<br /> +<span style="margin-left: 8em;">MATTHEW PRIOR.<br /></span> +</p> + +<p>Every game lends itself to the propounding of a variety of puzzles. +They can be made, as we have seen, out of the chessboard and the +peculiar moves of the chess pieces. I will now give just a few +examples of puzzles with playing cards and dominoes, and also go out +of doors and consider one or two little posers in the cricket field, +at the football match, and the horse race and motor-car race.</p> + +<hr style="width: 30%;" /> +<p><a name="X_378_DOMINOES_IN_PROGRESSION" id="X_378_DOMINOES_IN_PROGRESSION"></a><a href="#X_378_DOMINOES_IN_PROGRESSIONa"><b>378.—DOMINOES IN PROGRESSION.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q378.png" width="400" height="246" alt="" title="" /> +</div> + +<p>It will be seen that I have played six dominoes, in the illustration, +in accordance with the ordinary rules of the game, 4 against 4, 1 +against 1, and so on, and yet the sum of the spots on the successive +dominoes, 4, 5, 6, 7, 8, 9, are in arithmetical progression; that is, +the numbers taken in order have a common difference of 1. In how many +different ways may we play six dominoes, from an ordinary box of +twenty-eight, so that the numbers on them may lie in arithmetical +progression? We must always play from left to right, and numbers in +decreasing arithmetical progression (such as 9, 8, 7, 6, 5, 4) are not +admissible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_379_THE_FIVE_DOMINOES" id="X_379_THE_FIVE_DOMINOES"></a><a href="#X_379_THE_FIVE_DOMINOESa"><b>379.—THE FIVE DOMINOES.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q379.png" width="400" height="128" alt="" title="" /> +</div> + +<p>Here is a new little puzzle that is not difficult, but will probably +be found entertaining by my readers. It will be seen that the five +dominoes are so arranged in proper sequence (that is, with 1 against +1, 2 against 2, and so on), that the total number of pips on the two +end dominoes is five, and the sum of the pips on the three dominoes in +the middle is also five. There are just three other arrangements +giving five for the additions. They are: —</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>(1—0)</td><td align='center'>(0—0)</td><td align='center'>(0—2)</td><td align='center'>(2—1)</td><td align='left'>(1—3)</td></tr> +<tr><td align='center'>(4—0)</td><td align='center'>(0—0)</td><td align='center'>(0—2)</td><td align='center'>(2—1)</td><td align='left'>(1—0)</td></tr> +<tr><td align='center'>(2—0)</td><td align='center'>(0—0)</td><td align='center'>(0—1)</td><td align='center'>(1—3)</td><td align='left'>(3—0)</td></tr> +</table></div> + +<p>Now, how many similar arrangements are there of five dominoes that +shall give six instead of five in the two additions?</p> + +<hr style="width: 30%;" /> +<p><a name="X_380_THE_DOMINO_FRAME_PUZZLE" id="X_380_THE_DOMINO_FRAME_PUZZLE"></a><a href="#X_380_THE_DOMINO_FRAME_PUZZLEa"><b>380.—THE DOMINO FRAME PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q380.png" width="400" height="400" alt="" title="" /> +</div> + +<p>It will be seen in the illustration that the full set of twenty-eight +dominoes is arranged in the form of a square frame, with 6 against 6, +2 against 2, blank against blank, and so on, as in the game. It will +be found that the pips in the top row and left-hand column both add up +44. The pips in the other two sides sum to 59 and 32 respectively. The +puzzle is to rearrange the dominoes in the same form so that all of +the four sides shall sum to 44. Remember that the dominoes must be +correctly placed one against another as in the game.</p> + +<hr style="width: 30%;" /> +<p><a name="X_381_THE_CARD_FRAME_PUZZLE" id="X_381_THE_CARD_FRAME_PUZZLE"></a><a href="#X_381_THE_CARD_FRAME_PUZZLEa"><b>381.—THE CARD FRAME PUZZLE.</b></a></p> + +<p>In the illustration we have a frame constructed from the ten playing +cards, ace to ten of diamonds. The children who made it wanted the +pips on all four sides to add up alike, but they failed in their +attempt and gave it up as impossible. It will be seen that the pips in +the <span class='pagenum'>Pg 115<a name="Page_115" id="Page_115"></a></span>top row, the bottom row, and the left-hand side all add up 14, +but the right-hand side sums to 23. Now, what they were trying to do +is quite possible. Can you rearrange the ten cards in the same +formation so that all four sides shall add up alike? Of course they +need not add up 14, but any number you choose to select.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q381.png" width="400" height="510" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_382_THE_CROSS_OF_CARDS" id="X_382_THE_CROSS_OF_CARDS"></a><a href="#X_382_THE_CROSS_OF_CARDSa"><b>382.—THE CROSS OF CARDS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q382.png" width="400" height="430" alt="" title="" /> +</div> + +<p>In this case we use only nine cards—the ace to nine of diamonds. The +puzzle is to arrange them in the form of a cross, exactly in the way +shown in the illustration, so that the pips in the vertical bar and in +the horizontal bar add up alike. In the example given it will be found +that both directions add up 23. What I want to know is, how many +different ways are there of rearranging the cards in order to bring +about this result? It will be seen that, without affecting the +solution, we may exchange the 5 with the 6, the 5 with the 7, the 8 +with the 3, and so on. Also we may make the horizontal and the +vertical bars change places. But such obvious manipulations as these +are not to be regarded as different solutions. They are all mere +variations of one fundamental solution. Now, how many of these +fundamentally different solutions are there? The pips need not, of +course, always add up 23.</p> + +<hr style="width: 30%;" /> +<p><a name="X_383_THE_T_CARD_PUZZLE" id="X_383_THE_T_CARD_PUZZLE"></a><a href="#X_383_THE_T_CARD_PUZZLEa"><b>383.—THE "T" CARD PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q383.png" width="400" height="362" alt="" title="" /> +</div> + +<p>An entertaining little puzzle with cards is to take the nine cards of +a suit, from ace to nine inclusive, and arrange them in the form of +the letter "T," as shown in the illustration, so that the pips in the +horizontal line shall count the same as those in the column. In the +example given they add up twenty-three both ways. Now, it is quite +easy to get a single correct arrangement. The puzzle is to discover in +just how many different ways it may be done. Though the number is +high, the solution is not really difficult if we attack the puzzle in +the right manner. The reverse way obtained by reflecting the +illustration in a mirror we will not count as different, but all other +changes in the relative positions of the cards will here count. How +many different ways are there?</p> + +<hr style="width: 30%;" /> +<p><a name="X_384_CARD_TRIANGLES" id="X_384_CARD_TRIANGLES"></a><a href="#X_384_CARD_TRIANGLESa"><b>384.—CARD TRIANGLES.</b></a></p> + +<p>Here you pick out the nine cards, ace to nine of diamonds, and arrange +them in the form of a triangle, exactly as shown in the illustration, +so that the pips add up the same on the three sides. In the example +given it will be seen that they sum to 20 on each side, but the +particular number is of no importance so long as it is the same on all +three sides. The puzzle <span class='pagenum'>Pg 116<a name="Page_116" id="Page_116"></a></span>is to find out in just how many different +ways this can be done.</p> + +<p>If you simply turn the cards round so that one of the other two sides +is nearest to you this will not count as different, for the order will +be the same. Also, if you make the 4, 9, 5 change places with the 7, +3, 8, and at the same time exchange the 1 and the 6, it will not be +different. But if you only change the 1 and the 6 it will be +different, because the order round the triangle is not the same. This +explanation will prevent any doubt arising as to the conditions.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q384.png" width="400" height="389" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_385_STRAND_PATIENCE" id="X_385_STRAND_PATIENCE"></a><a href="#X_385_STRAND_PATIENCEa"><b>385.—"STRAND" PATIENCE.</b></a></p> + +<p>The idea for this came to me when considering the game of Patience +that I gave in the <i>Strand Magazine</i> for December, 1910, which has +been reprinted in Ernest Bergholt's <i>Second Book of Patience Games</i>, +under the new name of "King Albert."</p> + +<p>Make two piles of cards as follows: 9 D, 8 S, 7 D, 6 S, 5 D, 4 S, 3 +D, 2 S, 1 D, and 9 H, 8 C, 7 H, 6 C, 5 H, 4 C, 3 H, 2 C, 1 H, with the +9 of diamonds at the bottom of one pile and the 9 of hearts at the +bottom of the other. The point is to exchange the spades with the +clubs, so that the diamonds and clubs are still in numerical order in +one pile and the hearts and spades in the other. There are four vacant +spaces in addition to the two spaces occupied by the piles, and any +card may be laid on a space, but a card can only be laid on another of +the next higher value—an ace on a two, a two on a three, and so on. +Patience is required to discover the shortest way of doing this. When +there are four vacant spaces you can pile four cards in seven moves, +with only three spaces you can pile them in nine moves, and with two +spaces you cannot pile more than two cards. When you have a grasp of +these and similar facts you will be able to remove a number of cards +bodily and write down 7, 9, or whatever the number of moves may be. +The gradual shortening of play is fascinating, and first attempts are +surprisingly lengthy.</p> + +<hr style="width: 30%;" /> +<p><a name="X_386_A_TRICK_WITH_DICE" id="X_386_A_TRICK_WITH_DICE"></a><a href="#X_386_A_TRICK_WITH_DICEa"><b>386.—A TRICK WITH DICE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q386.png" width="400" height="151" alt="" title="" /> +</div> + +<p>Here is a neat little trick with three dice. I ask you to throw the +dice without my seeing them. Then I tell you to multiply the points of +the first die by 2 and add 5; then multiply the result by 5 and add +the points of the second die; then multiply the result by 10 and add +the points of the third die. You then give me the total, and I can at +once tell you the points thrown with the three dice. How do I do it? +As an example, if you threw 1, 3, and 6, as in the illustration, the +result you would give me would be 386, from which I could at once say +what you had thrown.</p> + +<hr style="width: 30%;" /> +<p><a name="X_387_THE_VILLAGE_CRICKET_MATCH" id="X_387_THE_VILLAGE_CRICKET_MATCH"></a><a href="#X_387_THE_VILLAGE_CRICKET_MATCHa"><b>387.—THE VILLAGE CRICKET MATCH.</b></a></p> + +<p>In a cricket match, Dingley Dell <i>v</i>. All Muggleton, the latter had +the first innings. Mr. Dumkins and Mr. Podder were at the wickets, +when the wary Dumkins made a splendid late cut, and Mr. Podder called +on him to run. Four runs were apparently completed, but the vigilant +umpires at each end called, "three short," making six short runs in +all. What number did Mr. Dumkins score? When Dingley Dell took their +turn at the wickets their champions were Mr. Luffey and Mr. Struggles. +The latter made a magnificent off-drive, and invited his colleague to +"come along," with the result that the observant spectators applauded +them for what was supposed to have been three sharp runs. But the +umpires declared that there had been two short runs at each end—four +in all. To what extent, if any, did this manœuvre increase Mr. +Struggles's total?</p> + +<hr style="width: 30%;" /> +<p><a name="X_388_SLOW_CRICKET" id="X_388_SLOW_CRICKET"></a><a href="#X_388_SLOW_CRICKETa"><b>388.—SLOW CRICKET.</b></a></p> + +<p>In the recent county match between Wessex and Nincomshire the former +team were at the wickets all day, the last man being put out a few +minutes before the time for drawing stumps. The play was so slow that +most of the spectators were fast asleep, and, on being awakened by one +of the officials clearing the ground, we learnt that two men had been +put out leg-before-wicket for a combined score of 19 runs; four men +were caught for a combined score or 17 runs; one man was run out for a +duck's egg; and the others were all bowled for 3 runs each. There were +no extras. We were not told which of the men was the captain, but he +made exactly 15 more than the average of his team. What was the +captain's score?</p> + +<hr style="width: 30%;" /> +<p><a name="X_389_THE_FOOTBALL_PLAYERS" id="X_389_THE_FOOTBALL_PLAYERS"></a><a href="#X_389_THE_FOOTBALL_PLAYERSa"><b>389.—THE FOOTBALL PLAYERS.</b></a></p> + +<p>"It is a glorious game!" an enthusiast was heard to exclaim. "At the +close of last season, <span class='pagenum'>Pg 117<a name="Page_117" id="Page_117"></a></span>of the footballers of my acquaintance four had +broken their left arm, five had broken their right arm, two had the +right arm sound, and three had sound left arms." Can you discover from +that statement what is the smallest number of players that the speaker +could be acquainted with?</p> + +<p>It does not at all follow that there were as many as fourteen men, +because, for example, two of the men who had broken the left arm might +also be the two who had sound right arms.</p> + +<hr style="width: 30%;" /> +<p><a name="X_390_THE_HORSE-RACE_PUZZLE" id="X_390_THE_HORSE-RACE_PUZZLE"></a><a href="#X_390_THE_HORSE-RACE_PUZZLEa"><b>390.—THE HORSE-RACE PUZZLE.</b></a></p> + +<p>There are no morals in puzzles. When we are solving the old puzzle of +the captain who, having to throw half his crew overboard in a storm, +arranged to draw lots, but so placed the men that only the Turks were +sacrificed, and all the Christians left on board, we do not stop to +discuss the questionable morality of the proceeding. And when we are +dealing with a measuring problem, in which certain thirsty pilgrims +are to make an equitable division of a barrel of beer, we do not +object that, as total abstainers, it is against our conscience to have +anything to do with intoxicating liquor. Therefore I make no apology +for introducing a puzzle that deals with betting.</p> + +<p>Three horses—Acorn, Bluebottle, and Capsule—start in a race. The +odds are 4 to 1, Acorn; 3 to 1, Bluebottle; 2 to 1, Capsule. Now, how +much must I invest on each horse in order to win £13, no matter which +horse comes in first? Supposing, as an example, that I betted £5 on +each horse. Then, if Acorn won, I should receive £20 (four times £5), +and have to pay £5 each for the other two horses; thereby winning £10. +But it will be found that if Bluebottle was first I should only win +£5, and if Capsule won I should gain nothing and lose nothing. This +will make the question perfectly clear to the novice, who, like +myself, is not interested in the calling of the fraternity who profess +to be engaged in the noble task of "improving the breed of horses."</p> + +<hr style="width: 30%;" /> +<p><a name="X_391_THE_MOTOR-CAR_RACE" id="X_391_THE_MOTOR-CAR_RACE"></a><a href="#X_391_THE_MOTOR-CAR_RACEa"><b>391.—THE MOTOR-CAR RACE.</b></a></p> + +<p>Sometimes a quite simple statement of fact, if worded in an unfamiliar +manner, will cause considerable perplexity. Here is an example, and it +will doubtless puzzle some of my more youthful readers just a little. +I happened to be at a motor-car race at Brooklands, when one spectator +said to another, while a number of cars were whirling round and round +the circular track:—</p> + +<p>"There's Gogglesmith—that man in the white car!"</p> + +<p>"Yes, I see," was the reply; "but how many cars are running in this +race?"</p> + +<p>Then came this curious rejoinder:—</p> + +<p>"One-third of the cars in front of Gogglesmith added to three-quarters +of those behind him will give you the answer."</p> + +<p>Now, can you tell how many cars were running in the race?</p> + + + +<hr style="width: 65%;" /> +<h2><a name="PUZZLE_GAMES" id="PUZZLE_GAMES"></a><a href="#CONTENTS">PUZZLE GAMES.</a></h2> + +<p class='center'> +"He that is beaten may be said<br /> +To lie in honour's truckle bed."<br /> +<span style="margin-left: 8em;">HUDIBRAS.<br /></span> +</p> + +<p>It may be said generally that a game is a contest of skill for two or +more persons, into which we enter either for amusement or to win a +prize. A puzzle is something to be done or solved by the individual. +For example, if it were possible for us so to master the complexities +of the game of chess that we could be assured of always winning with +the first or second move, as the case might be, or of always drawing, +then it would cease to be a game and would become a puzzle. Of course +among the young and uninformed, when the correct winning play is not +understood, a puzzle may well make a very good game. Thus there is no +doubt children will continue to play "Noughts and Crosses," though I +have shown (No. 109, "<i>Canterbury Puzzles</i>") that between two players +who both thoroughly understand the play, every game should be drawn. +Neither player could ever win except through the blundering of his +opponent. But I am writing from the point of view of the student of +these things.</p> + +<p>The examples that I give in this class are apparently games, but, +since I show in every case how one player may win if he only play +correctly, they are in reality puzzles. Their interest, therefore, +lies in attempting to discover the leading method of play.</p> + +<hr style="width: 30%;" /> +<p><a name="X_392_THE_PEBBLE_GAME" id="X_392_THE_PEBBLE_GAME"></a><a href="#X_392_THE_PEBBLE_GAMEa"><b>392.—THE PEBBLE GAME.</b></a></p> + +<p>Here is an interesting little puzzle game that I used to play with an +acquaintance on the beach at Slocomb-on-Sea. Two players place an odd +number of pebbles, we will say fifteen, between them. Then each takes +in turn one, two, or three pebbles (as he chooses), and the winner is +the one who gets the odd number. Thus, if you get seven and your +opponent eight, you win. If you get six and he gets nine, he wins. +Ought the first or second player to win, and how? When you have +settled the question with fifteen pebbles try again with, say, +thirteen.</p> + +<hr style="width: 30%;" /> +<p><a name="X_393_THE_TWO_ROOKS" id="X_393_THE_TWO_ROOKS"></a><a href="#X_393_THE_TWO_ROOKSa"><b>393.—THE TWO ROOKS.</b></a></p> + +<p>This is a puzzle game for two players. Each player has a single rook. +The first player places his rook on any square of the board that he +may choose to select, and then the second player does the same. They +now play in turn, the point of each play being to capture the +opponent's rook. But in this game you cannot play through a line of +attack without being captured. That is to say, if in the diagram it is +Black's turn to <span class='pagenum'>Pg 118<a name="Page_118" id="Page_118"></a></span>play, he cannot move his rook to his king's knight's +square, or to his king's rook's square, because he would enter the +"line of fire" when passing his king's bishop's square. For the same +reason he cannot move to his queen's rook's seventh or eighth squares. +Now, the game can never end in a draw. Sooner or later one of the +rooks must fall, unless, of course, both players commit the absurdity +of not trying to win. The trick of winning is ridiculously simple when +you know it. Can you solve the puzzle?</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q393.png" width="400" height="437" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_394_PUSS_IN_THE_CORNER" id="X_394_PUSS_IN_THE_CORNER"></a><a href="#X_394_PUSS_IN_THE_CORNERa"><b>394.—PUSS IN THE CORNER.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q394.png" width="400" height="398" alt="" title="" /> +</div> + +<p>This variation of the last puzzle is also played by two persons. One +puts a counter on No. 6, and the other puts one on No. 55, and they +play alternately by removing the counter to any other number in a +line. If your opponent moves at any time on to one of the lines you +occupy, or even crosses one of your lines, you immediately capture him +and win. We will take an illustrative game.</p> + +<p>A moves from 55 to 52; B moves from 6 to 13; A advances to 23; B goes +to 15; A retreats to 26; B retreats to 13; A advances to 21; B +retreats to 2; A advances to 7; B goes to 3; A moves to 6; B must now +go to 4; A establishes himself at 11, and B must be captured next move +because he is compelled to cross a line on which A stands. Play this +over and you will understand the game directly. Now, the puzzle part +of the game is this: Which player should win, and how many moves are +necessary?</p> + +<hr style="width: 30%;" /> +<p><a name="X_395_A_WAR_PUZZLE_GAME" id="X_395_A_WAR_PUZZLE_GAME"></a><a href="#X_395_A_WAR_PUZZLE_GAMEa"><b>395.—A WAR PUZZLE GAME.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q395.png" width="400" height="397" alt="" title="" /> +</div> + +<p>Here is another puzzle game. One player, representing the British +general, places a counter at B, and the other player, representing the +enemy, places his counter at E. The Britisher makes the first advance +along one of the roads to the next town, then the enemy moves to one +of his nearest towns, and so on in turns, until the British general +gets into the same town as the enemy and captures him. Although each +must always move along a road to the next town only, and the second +player may do his utmost to avoid capture, the British general (as we +should suppose, from the analogy of real life) must infallibly win. +But how? That is the question.</p> + +<hr style="width: 30%;" /> +<p><a name="X_396_A_MATCH_MYSTERY" id="X_396_A_MATCH_MYSTERY"></a><a href="#X_396_A_MATCH_MYSTERYa"><b>396.—A MATCH MYSTERY.</b></a></p> + +<p>Here is a little game that is childishly simple in its conditions. But +it is well worth investigation.</p> + +<p>Mr. Stubbs pulled a small table between himself and his friend, Mr. +Wilson, and took a box of matches, from which he counted out thirty.</p> + +<p>"Here are thirty matches," he said. "I <span class='pagenum'>Pg 119<a name="Page_119" id="Page_119"></a></span>divide them into three unequal +heaps. Let me see. We have 14, 11, and 5, as it happens. Now, the two +players draw alternately any number from any one heap, and he who +draws the last match loses the game. That's all! I will play with you, +Wilson. I have formed the heaps, so you have the first draw."</p> + +<p>"As I can draw any number," Mr. Wilson said, "suppose I exhibit my +usual moderation and take all the 14 heap."</p> + +<p>"That is the worst you could do, for it loses right away. I take 6 +from the 11, leaving two equal heaps of 5, and to leave two equal +heaps is a certain win (with the single exception of 1, 1), because +whatever you do in one heap I can repeat in the other. If you leave 4 +in one heap, I leave 4 in the other. If you then leave 2 in one heap, +I leave 2 in the other. If you leave only 1 in one heap, then I take +all the other heap. If you take all one heap, I take all but one in +the other. No, you must never leave two heaps, unless they are equal +heaps and more than 1, 1. Let's begin again."</p> + +<p>"Very well, then," said Mr. Wilson. "I will take 6 from the 14, and +leave you 8, 11, 5."</p> + +<p>Mr. Stubbs then left 8, 11, 3; Mr. Wilson, 8, 5, 3; Mr. Stubbs, 6, 5, +3; Mr. Wilson,4, 5, 3; Mr. Stubbs, 4, 5, 1; Mr. Wilson, 4, 3, 1; Mr. +Stubbs, 2, 3, 1; Mr. Wilson, 2, 1, 1; which Mr. Stubbs reduced to 1, +1, 1.</p> + +<p>"It is now quite clear that I must win," said Mr. Stubbs, because you +must take 1, and then I take 1, leaving you the last match. You never +had a chance. There are just thirteen different ways in which the +matches may be grouped at the start for a certain win. In fact, the +groups selected, 14, 11, 5, are a certain win, because for whatever +your opponent may play there is another winning group you can secure, +and so on and on down to the last match."</p> + +<hr style="width: 30%;" /> +<p><a name="X_397_THE_MONTENEGRIN_DICE_GAME" id="X_397_THE_MONTENEGRIN_DICE_GAME"></a><a href="#X_397_THE_MONTENEGRIN_DICE_GAMEa"><b>397.—THE MONTENEGRIN DICE GAME.</b></a></p> + +<p>It is said that the inhabitants of Montenegro have a little dice game +that is both ingenious and well worth investigation. The two players +first select two different pairs of odd numbers (always higher than 3) +and then alternately toss three dice. Whichever first throws the dice +so that they add up to one of his selected numbers wins. If they are +both successful in two successive throws it is a draw and they try +again. For example, one player may select 7 and 15 and the other 5 and +13. Then if the first player throws so that the three dice add up 7 or +15 he wins, unless the second man gets either 5 or 13 on his throw.</p> + +<p>The puzzle is to discover which two pairs of numbers should be +selected in order to give both players an exactly even chance.</p> + +<hr style="width: 30%;" /> +<p><a name="X_398_THE_CIGAR_PUZZLE" id="X_398_THE_CIGAR_PUZZLE"></a><a href="#X_398_THE_CIGAR_PUZZLEa"><b>398.—THE CIGAR PUZZLE.</b></a></p> + +<p>I once propounded the following puzzle in a London club, and for a +considerable period it absorbed the attention of the members. They +could make nothing of it, and considered it quite impossible of +solution. And yet, as I shall show, the answer is remarkably simple.</p> + +<p>Two men are seated at a square-topped table. One places an ordinary +cigar (flat at one end, pointed at the other) on the table, then the +other does the same, and so on alternately, a condition being that no +cigar shall touch another. Which player should succeed in placing the +last cigar, assuming that they each will play in the best possible +manner? The size of the table top and the size of the cigar are not +given, but in order to exclude the ridiculous answer that the table +might be so diminutive as only to take one cigar, we will say that the +table must not be less than 2 feet square and the cigar not more than +4½ inches long. With those restrictions you may take any dimensions +you like. Of course we assume that all the cigars are exactly alike in +every respect. Should the first player, or the second player, win?</p> + + + +<hr style="width: 65%;" /> +<h2><a name="MAGIC_SQUARE_PROBLEMS" id="MAGIC_SQUARE_PROBLEMS"></a><a href="#CONTENTS">MAGIC SQUARE PROBLEMS.</a></h2> + +<p class='center'> +"By magic numbers."<br /> +<span style="margin-left: 8em;">CONGREVE, <i>The Mourning Bride.</i></span><br /> +</p> + +<p>This is a very ancient branch of mathematical puzzledom, and it has an +immense, though scattered, literature of its own. In their simple form +of consecutive whole numbers arranged in a square so that every +column, every row, and each of the two long diagonals shall add up +alike, these magic squares offer three main lines of investigation: +Construction, Enumeration, and Classification. Of recent years many +ingenious methods have been devised for the construction of magics, +and the law of their formation is so well understood that all the +ancient mystery has evaporated and there is no longer any difficulty +in making squares of any dimensions. Almost the last word has been +said on this subject. The question of the enumeration of all the +possible squares of a given order stands just where it did over two +hundred years ago. Everybody knows that there is only one solution for +the third order, three cells by three; and Frénicle published in 1693 +diagrams of all the arrangements of the fourth order—880 in +number—and his results have been verified over and over again. I may +here refer to the general solution for this order, for numbers not +necessarily consecutive, by E. Bergholt in <i>Nature</i>, May 26, 1910, as +it is of the greatest importance to students of this subject. The +enumeration of the examples of any higher order is a completely +unsolved problem.</p> + +<p>As to classification, it is largely a matter of individual +taste—perhaps an æsthetic question, for there is beauty in the law +and order of numbers. A man once said that he divided the human race +into two great classes: those who take snuff and those who do not. I +am not <span class='pagenum'>Pg 120<a name="Page_120" id="Page_120"></a></span>sure that some of our classifications of magic squares are not +almost as valueless. However, lovers of these things seem somewhat +agreed that Nasik magic squares (so named by Mr. Frost, a student of +them, after the town in India where he lived, and also called +Diabolique and Pandiagonal) and Associated magic squares are of +special interest, so I will just explain what these are for the +benefit of the novice.</p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/msfig1.png" width="500" height="131" alt="" title="" /> +</div> + +<p>I published in <i>The Queen</i> for January 15, 1910, an article that would +enable the reader to write out, if he so desired, all the 880 magics +of the fourth order, and the following is the complete classification +that I gave. The first example is that of a Simple square that fulfils +the simple conditions and no more. The second example is a Semi-Nasik, +which has the additional property that the opposite short diagonals of +two cells each together sum to 34. Thus, 14 + 4 + 11 + 5 = 34 and 12 + +6 + 13 + 3 = 34. The third example is not only Semi-Nasik but <span class='pagenum'>Pg 121<a name="Page_121" id="Page_121"></a></span>also +Associated, because in it every number, if added to the number that is +equidistant, in a straight line, from the centre gives 17. Thus, 1 + +16, 2 + 15, 3 + 14, etc. The fourth example, considered the most +"perfect" of all, is a Nasik. Here all the broken diagonals sum to 34. +Thus, for example, 15 + 14 + 2 + 3, and 10 + 4 + 7 + 13, and 15 + 5 + +2 + 12. As a consequence, its properties are such that if you repeat +the square in all directions you may mark off a square, 4 × 4, +wherever you please, and it will be magic.</p> + +<p>The following table not only gives a complete enumeration under the +four forms described, but also a classification under the twelve +graphic types indicated in the diagrams. The dots at the end of each +line represent the relative positions of those complementary pairs, 1 ++ 16, 2 + 15, etc., which sum to 17. For example, it will be seen that +the first and second magic squares given are of Type VI., that the +third square is of Type III., and that the fourth is of Type I. +Edouard Lucas indicated these types, but he dropped exactly half of +them and did not attempt the classification.</p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/msfig2.png" width="500" height="427" alt="" title="" /> +</div> + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="2" summary=""> +<tr><td align='center'>NASIK</td><td align='left'>(Type I.)</td><td> </td><td> </td><td align='right'>48</td></tr> +<tr><td align='center'>SEMI-NASIK</td><td align='left'>(Type II., Transpositions of Nasik)</td><td> </td><td align='right'>48</td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type III., Associated)</td><td> </td><td align='right'>48</td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type IV.)</td><td align='right'>96</td><td> </td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type V.)</td><td align='right' class='bb'>96</td><td align='right'>192</td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type VI.)</td><td> </td><td align='right' class='bb'>96</td><td align='right'>384</td></tr> +<tr><td align='center'>SIMPLE.</td><td align='left'>(Type VI.)</td><td> </td><td align='right'>208</td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type VII.)</td><td align='right'>56</td><td> </td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type VIII.)</td><td align='right'>56</td><td> </td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type IX.)</td><td align='right'>56</td><td> </td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type X.)</td><td align='right' class='bb'>56</td><td align='right'>224</td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type XI.)</td><td align='right'>8</td><td> </td><td> </td></tr> +<tr><td align='center'>"</td><td align='left'>(Type XII.)</td><td align='right' class='bb'>8</td><td align='right' class='bb'>16</td><td align='right' class='bb'>448</td></tr> +<tr><td align='center'></td><td> </td><td> </td><td> </td><td align='left' class='bb'>880</td></tr> +</table></div> + +<p>It is hardly necessary to say that every one of these squares will +produce seven others by mere reversals and reflections, which we do +not count as different. So that there are 7,040 squares of this order, +880 of which are fundamentally different.</p> + +<p>An infinite variety of puzzles may be made introducing new conditions +into the magic square. In <i>The Canterbury Puzzles</i> I have given +examples of such squares with coins, with postage stamps, with +cutting-out conditions, and other tricks. I will now give a few +variants involving further novel conditions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_399_THE_TROUBLESOME_EIGHT" id="X_399_THE_TROUBLESOME_EIGHT"></a><a href="#X_399_THE_TROUBLESOME_EIGHTa"><b>399.—THE TROUBLESOME EIGHT.</b></a></p> + +<p>Nearly everybody knows that a "magic square" is an arrangement of +numbers in the form of a square so that every row, every column, and +each of the two long diagonals adds up alike. For example, you would +find little difficulty in merely placing a different number in each of +the nine cells in the illustration so that the rows, columns, and +diagonals shall all add up 15. And at your first attempt you will +probably find that you have an 8 in one of the corners. The puzzle is +to construct the magic square, under the same conditions, with the 8 +in the position shown.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q399.png" width="400" height="333" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_400_THE_MAGIC_STRIPS" id="X_400_THE_MAGIC_STRIPS"></a><a href="#X_400_THE_MAGIC_STRIPSa"><b>400.—THE MAGIC STRIPS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q400.png" width="400" height="504" alt="" title="" /> +</div> + +<p>I happened to have lying on my table a number of strips of cardboard, +with numbers printed on them from 1 upwards in numerical order. The +idea suddenly came to me, as ideas have a way of unexpectedly coming, +to make a little puzzle of this. I wonder whether many readers will +arrive at the same solution that I did.</p> + +<p>Take seven strips of cardboard and lay them together as above. Then +write on each of them the numbers 1, 2, 3, 4, 5, 6, 7, as shown, so +that the numbers shall form seven rows and seven columns.</p> + +<p>Now, the puzzle is to cut these strips into the fewest possible pieces +so that they may be placed together and form a magic square, the seven +rows, seven columns, and two diagonals adding up the same number. No +figures may <span class='pagenum'>Pg 122<a name="Page_122" id="Page_122"></a></span>be turned upside down or placed on their sides—that is, +all the strips must lie in their original direction.</p> + +<p>Of course you could cut each strip into seven separate pieces, each +piece containing a number, and the puzzle would then be very easy, but +I need hardly say that forty-nine pieces is a long way from being the +fewest possible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_401_EIGHT_JOLLY_GAOL_BIRDS" id="X_401_EIGHT_JOLLY_GAOL_BIRDS"></a><a href="#X_401_EIGHT_JOLLY_GAOL_BIRDSa"><b>401.—EIGHT JOLLY GAOL BIRDS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q401.png" width="400" height="398" alt="" title="" /> +</div> + +<p>The illustration shows the plan of a prison of nine cells all +communicating with one another by doorways. The eight prisoners have +their numbers on their backs, and any one of them is allowed to +exercise himself in whichever cell may happen to be vacant, subject to +the rule that at no time shall two prisoners be in the same cell. The +merry monarch in whose dominions the prison was situated offered them +special comforts one Christmas Eve if, without breaking that rule, +they could so place themselves that their numbers should form a magic +square.</p> + +<p>Now, prisoner No. 7 happened to know a good deal about magic squares, +so he worked out a scheme and naturally selected the method that was +most expeditious—that is, one involving the fewest possible moves +from cell to cell. But one man was a surly, obstinate fellow (quite +unfit for the society of his jovial companions), and he refused to +move out of his cell or take any part in the proceedings. But No. 7 +was quite equal to the emergency, and found that he could still do +what was required in the fewest possible moves without troubling the +brute to leave his cell. The puzzle is to show how he did it and, +incidentally, to discover which prisoner was so stupidly obstinate. +Can you find the fellow?</p> + +<hr style="width: 30%;" /> +<p><a name="X_402_NINE_JOLLY_GAOL_BIRDS" id="X_402_NINE_JOLLY_GAOL_BIRDS"></a><a href="#X_402_NINE_JOLLY_GAOL_BIRDSa"><b>402.—NINE JOLLY GAOL BIRDS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q402.png" width="400" height="398" alt="" title="" /> +</div> + +<p>Shortly after the episode recorded in the last puzzle occurred, a +ninth prisoner was placed in the vacant cell, and the merry monarch +then offered them all complete liberty on the following strange +conditions. They were required so to rearrange themselves in the cells +that their numbers formed a magic square without their movements +causing any two of them ever to be in the same cell together, except +that at the start one man was allowed to be placed on the shoulders of +another man, and thus add their numbers together, and move as one man. +For example, No. 8 might be placed on the shoulders of No. 2, and then +they would move about together as 10. The reader should seek first to +solve the puzzle in the fewest possible moves, and then see that the +man who is burdened has the least possible amount of work to do.</p> + +<hr style="width: 30%;" /> +<p><a name="X_403_THE_SPANISH_DUNGEON" id="X_403_THE_SPANISH_DUNGEON"></a><a href="#X_403_THE_SPANISH_DUNGEONa"><b>403.—THE SPANISH DUNGEON.</b></a></p> + +<p>Not fifty miles from Cadiz stood in the middle ages a castle, all +traces of which have for centuries disappeared. Among other +interesting features, this castle contained a particularly unpleasant +dungeon divided into sixteen cells, all communicating with one +another, as shown in the illustration.</p> + +<p>Now, the governor was a merry wight, and very fond of puzzles withal. +One day he went to the dungeon and said to the prisoners, "By my +halidame!" (or its equivalent in Spanish) "you shall all be set free +if you can solve this puzzle. You must so arrange yourselves in the +sixteen cells that the numbers on your backs shall form a magic square +in which every column, every row, and each of the two diagonals shall +add up the same. Only remember this: that in no case may two of you +ever be together in the same cell."</p> + +<p>One of the prisoners, after working at the problem for two or three +days, with a piece of chalk, undertook to obtain the liberty of +himself and his fellow-prisoners if they would follow his directions +and move through the doorway <span class='pagenum'>Pg 123<a name="Page_123" id="Page_123"></a></span>from cell to cell in the order in which +he should call out their numbers.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q403.png" width="400" height="398" alt="" title="" /> +</div> + +<p>He succeeded in his attempt, and, what is more remarkable, it would +seem from the account of his method recorded in the ancient manuscript +lying before me, that he did so in the fewest possible moves. The +reader is asked to show what these moves were.</p> + +<hr style="width: 30%;" /> +<p><a name="X_404_THE_SIBERIAN_DUNGEONS" id="X_404_THE_SIBERIAN_DUNGEONS"></a><a href="#X_404_THE_SIBERIAN_DUNGEONSa"><b>404.—THE SIBERIAN DUNGEONS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q404.png" width="400" height="200" alt="" title="" /> +</div> + +<p>The above is a trustworthy plan of a certain Russian prison in +Siberia. All the cells are numbered, and the prisoners are numbered +the same as the cells they occupy. The prison diet is so fattening +that these political prisoners are in perpetual fear lest, should +their pardon arrive, they might not be able to squeeze themselves +through the narrow doorways and get out. And of course it would be an +unreasonable thing to ask any government to pull down the walls of a +prison just to liberate the prisoners, however innocent they might be. +Therefore these men take all the healthy exercise they can in order to +retard their increasing obesity, and one of their recreations will +serve to furnish us with the following puzzle.</p> + +<p>Show, in the fewest possible moves, how the sixteen men may form +themselves into a magic square, so that the numbers on their backs +shall add up the same in each of the four columns, four rows, and two +diagonals without two prisoners having been at any time in the same +cell together. I had better say, for the information of those who have +not yet been made acquainted with these places, that it is a +peculiarity of prisons that you are not allowed to go outside their +walls. Any prisoner may go any distance that is possible in a single +move.</p> + +<hr style="width: 30%;" /> +<p><a name="X_405_CARD_MAGIC_SQUARES" id="X_405_CARD_MAGIC_SQUARES"></a><a href="#X_405_CARD_MAGIC_SQUARESa"><b>405.—CARD MAGIC SQUARES.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q405.png" width="400" height="539" alt="" title="" /> +</div> + +<p>Take an ordinary pack of cards and throw out the twelve court cards. +Now, with nine of the remainder (different suits are of no +consequence) form the above magic square. It will be seen that the +pips add up fifteen in every row in every column, and in each of the +two long diagonals. The puzzle is with the remaining cards (without +disturbing this arrangement) to form three more such magic squares, so +that each of the four shall add up to a different sum. There will, of +course, be four cards in the reduced pack that will not be used. These +four may be any that you choose. It is not a difficult puzzle, but +requires just a little thought.</p> + +<hr style="width: 30%;" /> +<p><a name="X_406_THE_EIGHTEEN_DOMINOES" id="X_406_THE_EIGHTEEN_DOMINOES"></a><a href="#X_406_THE_EIGHTEEN_DOMINOESa"><b>406.—THE EIGHTEEN DOMINOES.</b></a></p> + +<p>The illustration shows eighteen dominoes arranged in the form of a +square so that the pips in every one of the six columns, six rows, and +two long diagonals add up 13. This is the smallest summation possible +with any selection of dominoes from an ordinary box of twenty-eight. +The greatest possible summation is 23, and a solution for this number +may be easily obtained by substituting for every number its complement +to 6. Thus for every blank substitute a 6, for every 1 a 5, for every +2 a 4, for <span class='pagenum'>Pg 124<a name="Page_124" id="Page_124"></a></span>3 a 3, for 4 a 2, for 5 a 1, and for 6 a blank. But the +puzzle is to make a selection of eighteen dominoes and arrange them +(in exactly the form shown) so that the summations shall be 18 in all +the fourteen directions mentioned.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q406.png" width="400" height="393" alt="" title="" /> +</div> + + + +<hr style="width: 65%;" /> +<h2><a name="SUBTRACTING_MULTIPLYING_AND_DIVIDING_MAGICS" id="SUBTRACTING_MULTIPLYING_AND_DIVIDING_MAGICS"></a><a href="#CONTENTS">SUBTRACTING, MULTIPLYING, AND DIVIDING MAGICS.</a></h2> + +<p>Although the adding magic square is of such great antiquity, curiously +enough the multiplying magic does not appear to have been mentioned +until the end of the eighteenth century, when it was referred to +slightly by one writer and then forgotten until I revived it in +<i>Tit-Bits</i> in 1897. The dividing magic was apparently first discussed +by me in <i>The Weekly Dispatch</i> in June 1898. The subtracting magic is +here introduced for the first time. It will now be convenient to deal +with all four kinds of magic squares together.</p> + +<div class="figcenter" style="width: 550px;"> +<img src="images/magicfig1.png" width="550" height="145" alt="" title="" /> +</div> + +<p>In these four diagrams we have examples in the third order of adding, +subtracting, multiplying, and dividing squares. In the first the +constant, 15, is obtained by the addition of the rows, columns, and +two diagonals. In the second case you get the constant, 5, by +subtracting the first number in a line from the second, and the result +from the third. You can, of course, perform the operation in either +direction; but, in order to avoid negative numbers, it is more +convenient simply to deduct the middle number from the sum of the two +extreme numbers. This is, in effect, the same thing. It will be seen +that the constant of the adding square is <i>n</i> times that of the +subtracting square derived from it, where <i>n</i> is the number of cells +in the side of square. And the manner of derivation here is simply to +reverse the two diagonals. Both squares are "associated"—a term I +have explained in the introductory article to this department.</p> + +<p>The third square is a multiplying magic. The constant, 216, is +obtained by multiplying together the three numbers in any line. It is +"associated" by multiplication, instead of by addition. It is here +necessary to remark that in an adding square it is not essential that +the nine numbers should be consecutive. Write down any nine numbers in +this way—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>1</td><td align='right'>3</td><td align='right'>5</td></tr> +<tr><td align='right'>4</td><td align='right'>6</td><td align='right'>8</td></tr> +<tr><td align='right'>7</td><td align='right'>9</td><td align='right'>11</td></tr> +</table></div> + +<p>so that the horizontal differences are all alike and the vertical +differences also alike (here 2 and 3), and these numbers will form an +adding magic square. By making the differences 1 and 3 we, of course, +get consecutive numbers—a particular case, and nothing more. Now, in +the case of the multiplying square we must take these numbers in +geometrical instead of arithmetical progression, thus—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>1</td><td align='right'>3</td><td align='right'>9</td></tr> +<tr><td align='right'>2</td><td align='right'>6</td><td align='right'>18</td></tr> +<tr><td align='right'>4</td><td align='right'>12</td><td align='right'>36</td></tr> +</table></div> + +<p>Here each successive number in the rows is multiplied by 3, and in the +columns by 2. Had we multiplied by 2 and 8 we should get the regular +geometrical progression, 1, 2, 4, 8, 16, 32, 64, 128, and 256, but I +wish to avoid high numbers. The numbers are arranged in the square in +the same order as in the adding square.</p> + +<p>The fourth diagram is a dividing magic square. The constant 6 is here +obtained by dividing the second number in a line by the first (in +either direction) and the third number by the quotient. But, again, +the process is simplified by dividing the product of the two extreme +numbers by the middle number. This <span class='pagenum'>Pg 125<a name="Page_125" id="Page_125"></a></span>square is also "associated" by +multiplication. It is derived from the multiplying square by merely +reversing the diagonals, and the constant of the multiplying square is +the cube of that of the dividing square derived from it.</p> + +<p>The next set of diagrams shows the solutions for the fifth order of +square. They are all "associated" in the same way as before. The +subtracting square is derived from the adding square by reversing the +diagonals and exchanging opposite numbers in the centres of the +borders, and the constant of one is again <i>n</i> times that of the other. +The dividing square is derived from the multiplying square in the same +way, and the constant of the latter is the 5th power (that is the +<i>n</i>th) of that of the former.</p> + +<div class="figcenter" style="width: 550px;"> +<img src="images/magicfig2.png" width="550" height="629" alt="" title="" /> +</div> + +<p>These squares are thus quite easy for odd orders. But the reader will +probably find some difficulty over the even orders, concerning which I +will leave him to make his own researches, merely propounding two +little problems.</p> + +<hr style="width: 30%;" /> +<p><a name="X_407_TWO_NEW_MAGIC_SQUARES" id="X_407_TWO_NEW_MAGIC_SQUARES"></a><a href="#X_407_TWO_NEW_MAGIC_SQUARESa"><b>407.—TWO NEW MAGIC SQUARES.</b></a></p> + +<p>Construct a subtracting magic square with the first sixteen whole +numbers that shall be "associated" by <i>subtraction</i>. The constant is, +of course, obtained by subtracting the first number from the second in +line, the result from the third, and the result again from the fourth. +Also construct a dividing magic square of the same order that shall be +"associated" by <i>division</i>. The constant is obtained by dividing the +second number in a line by the first, the third by the quotient, and +the fourth by the next quotient.</p> + +<hr style="width: 30%;" /> +<p><a name="X_408_MAGIC_SQUARES_OF_TWO_DEGREES" id="X_408_MAGIC_SQUARES_OF_TWO_DEGREES"></a><a href="#X_408_MAGIC_SQUARES_OF_TWO_DEGREESa"><b>408.—MAGIC SQUARES OF TWO DEGREES.</b></a></p> + +<p>While reading a French mathematical work I happened to come across, +the following statement: "A very remarkable magic square of 8, in two +degrees, has been constructed by M. Pfeffermann. In other words, he +has managed to dispose the sixty-four first numbers on the squares of +a chessboard in such a way that the sum of the numbers in every line, +every column, and in each of the two diagonals, shall be the same; and +more, that if one substitutes for all the numbers their squares, the +square still remains magic." I at once set to work to solve this +problem, and, although it proved a very hard nut, one was rewarded by +the discovery of some curious and beautiful laws that govern it. The +reader may like to try his hand at the puzzle.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="MAGIC_SQUARES_OF_PRIMES" id="MAGIC_SQUARES_OF_PRIMES"></a><a href="#CONTENTS">MAGIC SQUARES OF PRIMES.</a></h2> + +<p>The problem of constructing magic squares with prime numbers only was +first discussed by myself in <i>The Weekly Dispatch</i> for 22nd July and +5th August 1900; but during the last three or four years it has +received great attention from American mathematicians. First, they +have sought to form these squares with the lowest possible constants. +Thus, the first nine prime numbers, 1 to 23 inclusive, sum to 99, +which (being divisible by 3) is theoretically a suitable series; yet +it has been demonstrated that the lowest possible constant is 111, and +the required series as follows: 1, 7, 13, 31, 37, 43, 61, 67, and 73. +Similarly, in the case of the fourth order, the lowest series of +primes that are "theoretically suitable" will not serve. But in every +other order, up to the 12th inclusive, magic squares have been +constructed with the lowest series of primes theoretically possible. +And the 12th is the lowest order in which a straight series of prime +numbers, unbroken, from 1 upwards has been made to work. In other +words, the first 144 odd prime numbers have actually been arranged in +magic form. The following summary is taken from <i>The Monist</i> (Chicago) +for October 1913:—</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>Order <br />of Square.</td><td align='right'>Totals <br />of Series.</td><td align='right'>Lowest <br />Constants.</td><td align='center'>Squares <br />made by—</td></tr> +<tr><td align='right'>3rd</td><td align='right'>333</td><td align='right'>111</td><td align='center'>Henry E. <br />Dudeney (1900).</td></tr> +<tr><td align='right'>4th</td><td align='right'>408</td><td align='right'>102</td><td align='center'>Ernest Bergholt<br />and C. D. Shuldham.</td></tr> +<tr><td align='right'>5th</td><td align='right'>1065</td><td align='right'>213</td><td align='center'>H. A. Sayles.</td></tr> +<tr><td align='right'>6th</td><td align='right'>2448</td><td align='right'>408</td><td align='center'>C. D. Shuldham <br />and J. N. Muncey.</td></tr> +<tr><td align='right'>7th</td><td align='right'>4893</td><td align='right'>699</td><td align='center'>do.</td></tr> +<tr><td align='right'>8th</td><td align='right'>8912</td><td align='right'>1114</td><td align='center'>do.</td></tr> +<tr><td align='right'>9th</td><td align='right'>15129</td><td align='right'>1681</td><td align='center'>do.</td></tr> +<tr><td align='right'>10th</td><td align='right'>24160</td><td align='right'>2416</td><td align='center'>J. N. Muncey.</td></tr> +<tr><td align='right'>11th</td><td align='right'>36095</td><td align='right'>3355</td><td align='center'>do.</td></tr> +<tr><td align='right'>12th</td><td align='right'>54168</td><td align='right'>4514</td><td align='center'>do.</td></tr> +</table></div> + + +<p>For further details the reader should consult the article itself, by +W. S. Andrews and H. A. Sayles.</p> + +<p><span class='pagenum'>Pg 126<a name="Page_126" id="Page_126"></a></span>These same investigators have also performed notable feats in +constructing associated and bordered prime magics, and Mr. Shuldham has +sent me a remarkable paper in which he gives examples of Nasik squares +constructed with primes for all orders from the 4th to the 10th, with +the exception of the 3rd (which is clearly impossible) and the 9th, +which, up to the time of writing, has baffled all attempts.</p> + +<hr style="width: 30%;" /> +<p><a name="X_409_THE_BASKETS_OF_PLUMS" id="X_409_THE_BASKETS_OF_PLUMS"></a><a href="#X_409_THE_BASKETS_OF_PLUMSa"><b>409.—THE BASKETS OF PLUMS.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q409.png" width="400" height="475" alt="" title="" /> +</div> + +<p>This is the form in which I first introduced the question of magic +squares with prime numbers. I will here warn the reader that there is +a little trap.</p> + +<p>A fruit merchant had nine baskets. Every basket contained plums (all +sound and ripe), and the number in every basket was different. When +placed as shown in the illustration they formed a magic square, so +that if he took any three baskets in a line in the eight possible +directions there would always be the same number of plums. This part +of the puzzle is easy enough to understand. But what follows seems at +first sight a little queer.</p> + +<p>The merchant told one of his men to distribute the contents of any +basket he chose among some children, giving plums to every child so +that each should receive an equal number. But the man found it quite +impossible, no matter which basket he selected and no matter how many +children he included in the treat. Show, by giving contents of the +nine baskets, how this could come about.</p> + +<hr style="width: 30%;" /> +<p><a name="X_410_THE_MANDARINS_T_PUZZLE" id="X_410_THE_MANDARINS_T_PUZZLE"></a><a href="#X_410_THE_MANDARINS_T_PUZZLEa"><b>410.—THE MANDARIN'S "T" PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q410.png" width="600" height="438" alt="" title="" /> +</div> + +<p>Before Mr. Beauchamp Cholmondely Marjoribanks set out on his tour in +the Far East, he prided himself on his knowledge of magic squares, a +subject that he had made his special hobby; but he soon discovered +that he had never really touched more than the fringe of the subject, +and that the wily Chinee could <span class='pagenum'>Pg 127<a name="Page_127" id="Page_127"></a></span>beat him easily. I present a little +problem that one learned mandarin propounded to our traveller, as +depicted on the last page.</p> + +<p>The Chinaman, after remarking that the construction of the ordinary +magic square of twenty-five cells is "too velly muchee easy," asked +our countryman so to place the numbers 1 to 25 in the square that +every column, every row, and each of the two diagonals should add up +65, with only prime numbers on the shaded "T." Of course the prime +numbers available are 1, 2, 3, 5, 7, 11, 13, 17, 19, and 23, so you +are at liberty to select any nine of these that will serve your +purpose. Can you construct this curious little magic square?</p> + +<hr style="width: 30%;" /> +<p><a name="X_411_A_MAGIC_SQUARE_OF_COMPOSITES" id="X_411_A_MAGIC_SQUARE_OF_COMPOSITES"></a><a href="#X_411_A_MAGIC_SQUARE_OF_COMPOSITESa"><b>411.—A MAGIC SQUARE OF COMPOSITES.</b></a></p> + +<p>As we have just discussed the construction of magic squares with prime +numbers, the following forms an interesting companion problem. Make a +magic square with nine consecutive composite numbers—the smallest +possible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_412_THE_MAGIC_KNIGHTS_TOUR" id="X_412_THE_MAGIC_KNIGHTS_TOUR"></a><a href="#X_412_THE_MAGIC_KNIGHTS_TOURa"><b>412.—THE MAGIC KNIGHT'S TOUR.</b></a></p> + +<p>Here is a problem that has never yet been solved, nor has its +impossibility been demonstrated. Play the knight once to every square +of the chessboard in a complete tour, numbering the squares in the +order visited, so that when completed the square shall be "magic," +adding up to 260 in every column, every row, and each of the two long +diagonals. I shall give the best answer that I have been able to +obtain, in which there is a slight error in the diagonals alone. Can a +perfect solution be found? I am convinced that it cannot, but it is +only a "pious opinion."</p> + + + +<hr style="width: 65%;" /> +<h2><a name="MAZES_AND_HOW_TO_THREAD_THEM" id="MAZES_AND_HOW_TO_THREAD_THEM"></a><a href="#CONTENTS">MAZES AND HOW TO THREAD THEM.</a></h2> + +<p class='center'> +"In wandering mazes lost."<br /> +<span style="margin-left: 8em;"><i>Paradise Lost.</i></span><br /> +</p> + +<p>The Old English word "maze," signifying a labyrinth, probably comes +from the Scandinavian, but its origin is somewhat uncertain. The late +Professor Skeat thought that the substantive was derived from the +verb, and as in old times to be mazed or amazed was to be "lost in +thought," the transition to a maze in whose tortuous windings we are +lost is natural and easy.</p> + +<p>The word "labyrinth" is derived from a Greek word signifying the +passages of a mine. The ancient mines of Greece and elsewhere inspired +fear and awe on account of their darkness and the danger of getting +lost in their intricate passages. Legend was afterwards built round +these mazes. The most familiar instance is the labyrinth made by +Dædalus in Crete for King Minos. In the centre was placed the +Minotaur, and no one who entered could find his way out again, but +became the prey of the monster. Seven youths and seven maidens were +sent regularly by the Athenians, and were duly devoured, until Theseus +slew the monster and escaped from the maze by aid of the clue of +thread provided by Ariadne; which accounts for our using to-day the +expression "threading a maze."</p> + +<p>The various forms of construction of mazes include complicated ranges +of caverns, architectural labyrinths, or sepulchral buildings, +tortuous devices indicated by coloured marbles and tiled pavements, +winding paths cut in the turf, and topiary mazes formed by clipped +hedges. As a matter of fact, they may be said to have descended to us +in precisely this order of variety.</p> + +<p>Mazes were used as ornaments on the state robes of Christian emperors +before the ninth century, and were soon adopted in the decoration of +cathedrals and other churches. The original idea was doubtless to +employ them as symbols of the complicated folds of sin by which man is +surrounded. They began to abound in the early part of the twelfth +century, and I give an illustration of one of this period in the +parish church at St. Quentin (Fig. 1). It formed a pavement of the +nave, and its diameter is 34½ feet. The path here is the line itself. +If you place your pencil at the point A and ignore the enclosing line, +the line leads you to the centre by a long route over the entire area; +but you never have any option as to direction during your course. As +we shall find in similar cases, these early ecclesiastical mazes were +generally not of a puzzle nature, but simply long, winding paths that +took you over practically all the ground enclosed.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig01.png" width="400" height="413" alt="FIG. 1.—Maze at St. Quentin." title="" /> +<span class="caption">FIG. 1.—Maze at St. Quentin.</span> +</div> + +<p>In the abbey church of St. Berlin, at St. Omer, is another of these +curious floors, representing the Temple of Jerusalem, with stations +for pilgrims. These mazes were actually visited and traversed by them +as a compromise for not going to the Holy Land in fulfilment of a vow. +They were also used as a means of penance, the penitent frequently +being directed to go the whole course of the maze on hands and knees.</p> + +<p><span class='pagenum'>Pg 128<a name="Page_128" id="Page_128"></a></span></p><div class="figcenter" style="width: 400px;"> +<img src="images/mzfig02.png" width="400" height="400" alt="FIG. 2.—Maze in Chartres Cathedral." title="" /> +<span class="caption">FIG. 2.—Maze in Chartres Cathedral.</span> +</div> + +<p>The maze in Chartres Cathedral, of which I give an illustration (Fig. +2), is 40 feet across, and was used by penitents following the +procession of Calvary. A labyrinth in Amiens Cathedral was octagonal, +similar to that at St. Quentin, measuring 42 feet across. It bore the +date 1288, but was destroyed in 1708. In the chapter-house at Bayeux +is a labyrinth formed of tiles, red, black, and encaustic, with a +pattern of brown and yellow. Dr. Ducarel, in his "<i>Tour through Part of +Normandy</i>" (printed in 1767), mentions the floor of the great +guard-chamber in the abbey of St. Stephen, at Caen, "the middle +whereof represents a maze or labyrinth about 10 feet diameter, and so +artfully contrived that, were we to suppose a man following all the +intricate meanders of its volutes, he could not travel less than a +mile before he got from one end to the other."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig03.png" width="400" height="398" alt="FIG. 3.—Maze in Lucca Cathedral." title="" /> +<span class="caption">FIG. 3.—Maze in Lucca Cathedral.</span> +</div> + +<p>Then these mazes were sometimes reduced in size and represented on a +single tile (Fig. 3). I give an example from Lucca Cathedral. It is on +one of the porch piers, and is 19½ inches in diameter. A writer in +1858 says that, "from the continual attrition it has received from +thousands of tracing fingers, a central group of Theseus and the +Minotaur has now been very nearly effaced." Other examples were, and +perhaps still are, to be found in the Abbey of Toussarts, at +Châlons-sur-Marne, in the very ancient church of St. Michele at Pavia, +at Aix in Provence, in the cathedrals of Poitiers, Rheims, and Arras, +in the church of Santa Maria in Aquiro in Rome, in San Vitale at +Ravenna, in the Roman mosaic pavement found at Salzburg, and +elsewhere. These mazes were sometimes called "Chemins de Jerusalem," +as being emblematical of the difficulties attending a journey to the +earthly Jerusalem and of those encountered by the Christian before he +can reach the heavenly Jerusalem—where the centre was frequently +called "Ciel."</p> + +<p>Common as these mazes were upon the Continent, it is probable that no +example is to be found in any English church; at least I am not aware +of the existence of any. But almost every county has, or has had, its +specimens of <span class='pagenum'>Pg 129<a name="Page_129" id="Page_129"></a></span>mazes cut in the turf. Though these are frequently known +as "miz-mazes" or "mize-mazes," it is not uncommon to find them +locally called "Troy-towns," "shepherds' races," or "Julian's +Bowers"—names that are misleading, as suggesting a false origin. From +the facts alone that many of these English turf mazes are clearly +copied from those in the Continental churches, and practically all are +found close to some ecclesiastical building or near the site of an +ancient one, we may regard it as certain that they were of church +origin and not invented by the shepherds or other rustics. And +curiously enough, these turf mazes are apparently unknown on the +Continent. They are distinctly mentioned by Shakespeare:—</p> + +<div class="poem"><div class="stanza"> +<span class="i0">"The nine men's morris is filled up with mud,<br /></span> +<span class="i0">And the quaint mazes in the wanton green<br /></span> +<span class="i0">For lack of tread are undistinguishable."<br /></span> +</div><div class="stanza"> +<span class="i0"><i>A Midsummer Night's Dream</i>, ii. 1.<br /></span><br /><br /> +</div></div> + +<div class="poem"><div class="stanza"> +<span class="i0">"My old bones ache: here's a maze trod indeed,<br /></span> +<span class="i0">Through forth-rights and meanders!"<br /></span> +</div><div class="stanza"> +<span class="i0"><i>The Tempest</i>, iii. 3.<br /></span> +</div></div> + +<p>There was such a maze at Comberton, in Cambridgeshire, and another, +locally called the "miz-maze," at Leigh, in Dorset. The latter was on +the highest part of a field on the top of a hill, a quarter of a mile +from the village, and was slightly hollow in the middle and enclosed +by a bank about 3 feet high. It was circular, and was thirty paces in +diameter. In 1868 the turf had grown over the little trenches, and it +was then impossible to trace the paths of the maze. The Comberton one +was at the same date believed to be perfect, but whether either or +both have now disappeared I cannot say. Nor have I been able to verify +the existence or non-existence of the other examples of which I am +able to give illustrations. I shall therefore write of them all in the +past tense, retaining the hope that some are still preserved.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig04.png" width="400" height="400" alt="FIG. 4.—Maze at Saffron Walden, Essex." title="" /> +<span class="caption">FIG. 4.—Maze at Saffron Walden, Essex.</span> +</div> + +<p>In the next two mazes given—that at Saffron Walden, Essex (110 feet +in diameter, Fig. 4), and the one near St. Anne's Well, at Sneinton, +Nottinghamshire (Fig. 5), which was ploughed up on February 27th, 1797 +(51 feet in diameter, with a path 535 yards long)—the paths must in +each case be understood to be on the lines, black or white, as the +case may be.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig05.png" width="400" height="402" alt="FIG. 5.—Maze at Sneinton, Nottinghamshire." title="" /> +<span class="caption">FIG. 5.—Maze at Sneinton, Nottinghamshire.</span> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig06.png" width="400" height="398" alt="FIG. 6.—Maze at Alkborough, Lincolnshire." title="" /> +<span class="caption">FIG. 6.—Maze at Alkborough, Lincolnshire.</span> +</div> + +<p>I give in Fig. 6 a maze that was at Alkborough, Lincolnshire, +overlooking the Humber. This was 44 feet in diameter, and the +resem<span class='pagenum'>Pg 130<a name="Page_130" id="Page_130"></a></span>blance between it and the mazes at Chartres and Lucca (Figs. 2 +and 3) will be at once perceived. A maze at Boughton Green, in +Nottinghamshire, a place celebrated at one time for its fair (Fig. 7), +was 37 feet in diameter. I also include the plan (Fig. 8) of one that +used to be on the outskirts of the village of Wing, near Uppingham, +Rutlandshire. This maze was 40 feet in diameter.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig07.png" width="400" height="396" alt="FIG. 7.—Maze at Boughton Green, Nottinghamshire." title="" /> +<span class="caption">FIG. 7.—Maze at Boughton Green, Nottinghamshire.</span> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig08.png" width="400" height="405" alt="FIG. 8.—Maze at Wing, Rutlandshire." title="" /> +<span class="caption">FIG. 8.—Maze at Wing, Rutlandshire.</span> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig09.png" width="400" height="398" alt="FIG. 9.—Maze on St. Catherine's Hill, Winchester." title="" /> +<span class="caption">FIG. 9.—Maze on St. Catherine's Hill, Winchester.</span> +</div> + +<p>The maze that was on St. Catherine's Hill, Winchester, in the parish +of Chilcombe, was a poor specimen (Fig. 9), since, as will be seen, +there was one short direct route to the centre, unless, as in Fig. 10 +again, the path is the line itself from end to end. This maze was 86 +feet square, cut in the turf, and was locally known as the +"Mize-maze." It became very indistinct about 1858, and was then recut +by the Warden of Winchester, with the aid of a plan possessed by a +lady living in the neighbourhood.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig10.png" width="400" height="397" alt="FIG. 10.—Maze on Ripon Common." title="" /> +<span class="caption">FIG. 10.—Maze on Ripon Common.</span> +</div> + +<p>A maze formerly existed on Ripon Common, in Yorkshire (Fig. 10). It +was ploughed up in 1827, but its plan was fortunately preserved. This +example was 20 yards in diameter, and its path is said to have been +407 yards long.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig11.png" width="400" height="400" alt="FIG. 11.—Maze at Theobalds, Hertfordshire." title="" /> +<span class="caption">FIG. 11.—Maze at Theobalds, Hertfordshire.</span> +</div> + +<p>In the case of the maze at Theobalds, Hertfordshire, after you have +found the entrance within the four enclosing hedges, the path is +<span class='pagenum'>Pg 131<a name="Page_131" id="Page_131"></a></span>forced (Fig. 11). As further illustrations of this class of maze, I +give one taken from an Italian work on architecture by Serlio, +published in 1537 (Fig. 12), and one by London and Wise, the designers +of the Hampton Court maze, from their book, <i>The Retired Gard'ner</i>, +published in 1706 (Fig. 13). Also, I add a Dutch maze (Fig. 14).</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig12.png" width="400" height="395" alt="FIG. 12.—Italian Maze of Sixteenth Century." title="" /> +<span class="caption">FIG. 12.—Italian Maze of Sixteenth Century.</span> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig13.png" width="400" height="272" alt="FIG. 13.—By the Designers of Hampton Court Maze." title="" /> +<span class="caption">FIG. 13.—By the Designers of Hampton Court Maze.</span> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig14.png" width="400" height="362" alt="FIG. 14.—A Dutch Maze." title="" /> +<span class="caption">FIG. 14.—A Dutch Maze.</span> +</div> + +<p>So far our mazes have been of historical interest, but they have +presented no difficulty in threading. After the Reformation period we +find mazes converted into mediums for recreation, and they generally +consisted of labyrinthine paths enclosed by thick and carefully +trimmed hedges. These topiary hedges were known to the Romans, with +whom the <i>topiarius</i> was the ornamental gardener. This type of maze +has of late years degenerated into the seaside "Puzzle Gardens. Teas, +sixpence, including admission to the Maze." The Hampton Court Maze, +sometimes called the "Wilderness," at the royal palace, was designed, +as I have said, by London and Wise for William III., who had a liking +for such things (Fig. 15). I have before me some three or four +versions of it, all slightly different from one another; but the plan +I select is taken from an old guide-book to the palace, and therefore +ought to be trustworthy. The meaning of the dotted lines, etc., will +be explained later on.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/mzfig15.png" width="600" height="248" alt="FIG. 15.—Maze at Hampton Court Palace." title="" /> +<span class="caption">FIG. 15.—Maze at Hampton Court Palace.</span> +</div> + +<div class="figcenter" style="width: 600px;"> +<img src="images/mzfig16.png" width="600" height="369" alt="FIG. 16.—Maze at Hatfield House, Herts." title="" /> +<span class="caption">FIG. 16.—Maze at Hatfield House, Herts.</span> +</div> + +<p>The maze at Hatfield House (Fig. 16), the seat of the Marquis of +Salisbury, like so many labyrinths, is not difficult on paper; but +both <span class='pagenum'>Pg 132<a name="Page_132" id="Page_132"></a></span>this and the Hampton Court Maze may prove very puzzling to +actually thread without knowing the plan. One reason is that one is so +apt to go down the same blind alleys over and over again, if one +proceeds without method. The maze planned by the desire of the Prince +Consort for the Royal Horticultural Society's Gardens at South +Kensington was allowed to go to ruin, and was then destroyed—no great +loss, for it was a feeble thing. It will be seen that there were three +entrances from the outside (Fig. 17), but the way to the centre is +very easy to discover. I include a German maze that is curious, but +not difficult to thread on paper (Fig. 18). The example of a labyrinth +formerly existing at Pimperne, in Dorset, is in a class by itself +(Fig. 19). It was formed of small ridges about a foot high, and +covered nearly an <span class='pagenum'>Pg 133<a name="Page_133" id="Page_133"></a></span>acre of ground; but it was, unfortunately, ploughed +up in 1730.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig17.png" width="400" height="590" alt="FIG. 17.—Maze formerly at South Kensington." title="" /> +<span class="caption">FIG. 17.—Maze formerly at South Kensington.</span> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig18.png" width="400" height="278" alt="FIG. 18.—A German Maze." title="" /> +<span class="caption">FIG. 18.—A German Maze.</span> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig19.png" width="400" height="404" alt="FIG. 19.—Maze at Pimperne, Dorset." title="" /> +<span class="caption">FIG. 19.—Maze at Pimperne, Dorset.</span> +</div> + +<p>We will now pass to the interesting subject of how to thread any maze. +While being necessarily brief, I will try to make the matter clear to +readers who have no knowledge of mathematics. And first of all we will +assume that we are trying to enter a maze (that is, get to the +"centre") of which we have no plan and about which we know nothing. +The first rule is this: If a maze has no parts of its hedges detached +from the rest, then if we always keep in touch with the hedge with the +right hand (or always touch it with the left), going down to the stop +in every blind alley and coming back on the other side, we shall pass +through every part of the maze and make our exit where we went in. +Therefore we must at one time or another enter the centre, and every +alley will be traversed twice.</p> + +<p>Now look at the Hampton Court plan. Follow, say to the right, the path +indicated by the <span class='pagenum'>Pg 134<a name="Page_134" id="Page_134"></a></span>dotted line, and what I have said is clearly correct +if we obliterate the two detached parts, or "islands," situated on +each side of the star. But as these islands are there, you cannot by +this method traverse every part of the maze; and if it had been so +planned that the "centre" was, like the star, between the two islands, +you would never pass through the "centre" at all. A glance at the +Hatfield maze will show that there are three of these detached hedges +or islands at the centre, so this method will never take you to the +"centre" of that one. But the rule will at least always bring you +safely out again unless you blunder in the following way. Suppose, +when you were going in the direction of the arrow in the Hampton Court +Maze, that you could not distinctly see the turning at the bottom, +that you imagined you were in a blind alley and, to save time, crossed +at once to the opposite hedge, then you would go round and round that +U-shaped island with your right hand still always on the hedge—for +ever after!</p> + +<p>This blunder happened to me a few years ago in a little maze on the +isle of Caldy, South Wales. I knew the maze was a small one, but after +a very long walk I was amazed to find that I did not either reach the +"centre" or get out again. So I threw a piece of paper on the ground, +and soon came round to it; from which I knew that I had blundered over +a supposed blind alley and was going round and round an island. +Crossing to the opposite hedge and using more care, I was quickly at +the centre and out again. Now, if I had made a similar mistake at +Hampton Court, and discovered the error when at the star, I should +merely have passed from one island to another! And if I had again +discovered that I was on a detached part, I might with ill luck have +recrossed to the first island again! We thus see that this "touching +the hedge" method should always bring us safely out of a maze that we +have entered; it may happen to take us through the "centre," and if we +miss the centre we shall know there must be islands. But it has to be +<span class='pagenum'>Pg 135<a name="Page_135" id="Page_135"></a></span>done with a little care, and in no case can we be sure that we have +traversed every alley or that there are no detached parts.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/mzfig20.png" width="400" height="374" alt="FIG. 20.—M. Tremaux's Method of Solution." title="" /> +<span class="caption">FIG. 20.—M. Tremaux's Method of Solution.</span> +</div> + +<p>If the maze has many islands, the traversing of the whole of it may be +a matter of considerable difficulty. Here is a method for solving any +maze, due to M. Trémaux, but it necessitates carefully marking in some +way your entrances and exits where the galleries fork. I give a +diagram of an imaginary maze of a very simple character that will +serve our purpose just as well as something more complex (Fig. 20). +The circles at the regions where we have a choice of turnings we may +call nodes. A "new" path or node is one that has not been entered +before on the route; an "old" path or node is one that has already +been entered, 1. No path may be traversed more than twice. 2. When you +come to a new node, take any path you like. 3. When by a new path you +come to an old node or to the stop of a blind alley, return by the +path you came. 4. When by an old path you come to an old node, take a +new path if there is one; if not, an old path. The route indicated by +the dotted line in the diagram is taken in accordance with these +simple rules, and it will be seen that it leads us to the centre, +although the maze consists of four islands.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/mzfig21.png" width="600" height="367" alt="FIG. 21.—How to thread the Hatfield Maze." title="" /> +<span class="caption">FIG. 21.—How to thread the Hatfield Maze.</span> +</div> + +<p><span class='pagenum'>Pg 136<a name="Page_136" id="Page_136"></a></span>Neither of the methods I have given will disclose to us the shortest +way to the centre, nor the number of the different routes. But we can +easily settle these points with a plan. Let us take the Hatfield maze +(Fig. 21). It will be seen that I have suppressed all the blind alleys +by the shading. I begin at the stop and work backwards until the path +forks. These shaded parts, therefore, can never be entered without our +having to retrace our steps. Then it is very clearly seen that if we +enter at A we must come out at B; if we enter at C we must come out at +D. Then we have merely to determine whether A, B, E, or C, D, E, is +the shorter route. As a matter of fact, it will be found by rough +measurement or calculation that the shortest route to the centre is by +way of C, D, E, F.</p> + +<p>I will now give three mazes that are simply puzzles on paper, for, so +far as I know, they have never been constructed in any other way. The +first I will call the Philadelphia maze (Fig. 22). Fourteen years ago +a travelling salesman, <span class='pagenum'>Pg 137<a name="Page_137" id="Page_137"></a></span>living in Philadelphia, U.S.A., developed a +curiously unrestrained passion for puzzles. He neglected his business, +and soon his position was taken from him. His days and nights were now +passed with the subject that fascinated him, and this little maze +seems to have driven him into insanity. He had been puzzling over it +for some time, and finally it sent him mad and caused him to fire a +bullet through his brain. Goodness knows what his difficulties could +have been! But there can be little doubt that he had a disordered +mind, and that if this little puzzle had not caused him to lose his +mental balance some other more or less trivial thing would in time +have done so. There is no moral in the story, unless it be that of the +Irish maxim, which applies to every occupation of life as much as to +the solving of puzzles: "Take things aisy; if you can't take them +aisy, take them as aisy as you can." And it is a bad and empirical way +of solving any puzzle—by blowing your brains out.</p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/mzfig22.png" width="500" height="516" alt="FIG. 22. The Philadelphia Maze, and its Solution." title="" /> +<span class="caption">FIG. 22. The Philadelphia Maze, and its Solution.</span> +</div> + +<p>Now, how many different routes are there from A to B in this maze if +we must never in any route go along the same passage twice? The four +open spaces where four passages end are not reckoned as "passages." In +the diagram (Fig. 22) it will be seen that I have again suppressed the +blind alleys. It will be found that, in any case, we must go from A to +C, and also from F to B. But when we have arrived at C there are three +ways, marked 1, 2, 3, of getting to D. Similarly, when we get to E +there are three ways, marked 4, 5, 6, of getting to F. We have also +the dotted route from C to E, the other dotted route from D to F, and +the passage from D to E, indicated by stars. We can, therefore, +express the position of affairs by the little diagram annexed (Fig. +23). Here every condition of route exactly corresponds to that in the +circular maze, only it is much less confusing to the eye. Now, the +number of routes, under the conditions, from A to B on this simplified +diagram is 640, and that is the required answer to the maze puzzle.</p> + +<div class="figcenter" style="width: 396px;"> +<img src="images/mzfig23.png" width="396" height="93" alt="FIG. 23.—Simplified Diagram of Fig. 22." title="" /> +<span class="caption">FIG. 23.—Simplified Diagram of Fig. 22.</span> +</div> +<p><br /></p> +<div class="figcenter" style="width: 500px;"> +<img src="images/mzfig24.png" width="500" height="510" alt="FIG. 24.—Can you find the Shortest Way to Centre?" title="" /> +<span class="caption">FIG. 24.—Can you find the Shortest Way to Centre?</span> +</div> + +<p>Finally, I will leave two easy maze puzzles (Figs. 24, 25) for my +readers to solve for themselves. The puzzle in each case is to find +the shortest possible route to the centre. Everybody knows the story +of Fair Rosamund and the Woodstock maze. What the maze was like or +whether it ever existed except in imagination is not known, many +writers believing that it was simply a badly-constructed house with a +large number of confusing rooms and passages. At any rate, my sketch +lacks the authority of the other mazes in this article. My "Rosamund's +Bower" is simply designed to show that where you have the plan before +you it often happens that the easiest way to find a route into a maze +is by working backwards and first finding a way out.</p> + +<div class="figcenter" style="width: 550px;"> +<img src="images/mzfig25.png" width="550" height="669" alt="FIG. 25.—Rosamund's Bower." title="" /> +<span class="caption">FIG. 25.—Rosamund's Bower.</span> +</div> + +<hr style="width: 65%;" /> +<h2><a name="THE_PARADOX_PARTY" id="THE_PARADOX_PARTY"></a><a href="#CONTENTS">THE PARADOX PARTY.</a></h2> + +<p class='center'> +"Is not life itself a paradox?"<br /> +<span style="margin-left: 8em;">C.L. DODGSON, <i>Pillow Problems</i>.</span><br /> +</p> + + +<p>"It is a wonderful age!" said Mr. Allgood, and everybody at the table +turned towards him and assumed an attitude of expectancy.</p> + +<p>This was an ordinary Christmas dinner of the Allgood family, with a +sprinkling of local friends. Nobody would have supposed that the above +remark would lead, as it did, to a succession of curious puzzles and +paradoxes, to which every member of the party contributed something of +interest. The little symposium was quite unpremeditated, so we must +not be too critical respecting a few of the posers that were +forthcoming. The varied character of the contributions is just what we +would expect on such an occasion, for it was a gathering not of expert +mathematicians and logicians, but of quite ordinary folk.</p> + +<p>"It is a wonderful age!" repeated Mr. Allgood. "A man has just +designed a square house in such a cunning manner that all the windows +on the four sides have a south aspect."</p> + +<p>"That would appeal to me," said Mrs. Allgood, "for I cannot endure a +room with a north aspect."</p> + +<p>"I cannot conceive how it is done," Uncle John confessed. "I suppose +he puts bay windows on the east and west sides; but how on earth can +be contrive to look south from the north side? Does he use mirrors, or +something of that kind?"</p> + +<p>"No," replied Mr. Allgood, "nothing of the sort. All the windows are +flush with the walls, and yet you get a southerly prospect from every +one of them. You see, there is no real difficulty in designing the +house if you select the proper spot for its erection. Now, this house +is designed for a gentleman who proposes to build it exactly at the +North Pole. If you think a moment you will realize that when you stand +at the North Pole it is impossible, no matter which way you may turn, +to look elsewhere than due south! There are no such directions as +north, east, or west when you are exactly at the North Pole. +Everything is due south!"</p> + +<p>"I am afraid, mother," said her son George, after the laughter had +subsided, "that, however much you might like the aspect, the situation +would be a little too bracing for you."</p> + +<p>"Ah, well!" she replied. "Your Uncle John fell also into the trap. I +am no good at catches and puzzles. I suppose I haven't the right sort +of brain. Perhaps some one will explain this to me. Only last week I +remarked to my hairdresser that it had been said that there are more +persons in the world than any one of them has hairs on his head. He +replied, 'Then it follows, madam, that two persons, at least, must +have exactly the same number of <span class='pagenum'>Pg 138<a name="Page_138" id="Page_138"></a></span>hairs on their heads.' If this is a +fact, I confess I cannot see it."</p> + +<p>"How do the bald-headed affect the question?" asked Uncle John.</p> + +<p>"If there are such persons in existence," replied Mrs. Allgood, "who +haven't a solitary hair on their heads discoverable under a +magnifying-glass, we will leave them out of the question. Still, I +don't see how you are to prove that at least two persons have exactly +the same number to a hair."</p> + +<p>"I think I can make it clear," said Mr. Filkins, who had dropped in +for the evening. "Assume the population of the world to be only one +million. Any number will do as well as another. Then your statement +was to the effect that no person has more than nine hundred and +ninety-nine thousand nine hundred and ninety-nine hairs on his head. +Is that so?"</p> + +<p>"Let me think," said Mrs. Allgood. "Yes—yes—that is correct."</p> + +<p>"Very well, then. As there are only nine hundred and ninety-nine +thousand nine hundred and ninety-nine <i>different</i> ways of bearing +hair, it is clear that the millionth person must repeat one of those +ways. Do you see?"</p> + +<p>"Yes; I see that—at least I think I see it."</p> + +<p>"Therefore two persons at least must have the same number of hairs on +their heads; and as the number of people on the earth so greatly +exceeds the number of hairs on any one person's head, there must, of +course, be an immense number of these repetitions."</p> + +<p>"But, Mr. Filkins," said little Willie Allgood, "why could not the +millionth man have, say, ten thousand hairs and a half?"</p> + +<p>"That is mere hair-splitting, Willie, and does not come into the +question."</p> + +<p>"Here is a curious paradox," said George. "If a thousand soldiers are +drawn up in battle array on a plane"—they understood him to mean +"plain"—"only one man will stand upright."</p> + +<p>Nobody could see why. But George explained that, according to Euclid, +a plane can touch a sphere only at one point, and that person only who +stands at that point, with respect to the centre of the earth, will +stand upright.</p> + +<p>"In the same way," he remarked, "if a billiard-table were quite +level—that is, a perfect plane—the balls ought to roll to the +centre."</p> + +<p>Though he tried to explain this by placing a visiting-card on an +orange and expounding the law of gravitation, Mrs. Allgood declined to +accept the statement. She could not see that the top of a true +billiard-table must, theoretically, be spherical, just like a portion +of the orange-peel that George cut out. Of course, the table is so +small in proportion to the surface of the earth that the curvature is +not appreciable, but it is nevertheless true in theory. A surface that +we call level is not the same as our idea of a true geometrical plane.</p> + +<p>"Uncle John," broke in Willie Allgood, "there is a certain island +situated between England and France, and yet that island is farther +from France than England is. What is the island?"</p> + +<p>"That seems absurd, my boy; because if I place this tumbler, to +represent the island, between these two plates, it seems impossible +that the tumbler can be farther from either of the plates than they +are from each other."</p> + +<p>"But isn't Guernsey between England and France?" asked Willie.</p> + +<p>"Yes, certainly."</p> + +<p>"Well, then, I think you will find, uncle, that Guernsey is about +twenty-six miles from France, and England is only twenty-one miles +from France, between Calais and Dover."</p> + +<p>"My mathematical master," said George, "has been trying to induce me +to accept the axiom that 'if equals be multiplied by equals the +products are equal.'"</p> + +<p>"It is self-evident," pointed out Mr. Filkins. "For example, if 3 feet +equal 1 yard, then twice 3 feet will equal 2 yards. Do you see?"</p> + +<p>"But, Mr. Filkins," asked George, "is this tumbler half full of water +equal to a similar glass half empty?"</p> + +<p>"Certainly, George."</p> + +<p>"Then it follows from the axiom that a glass full must equal a glass +empty. Is that correct?"</p> + +<p>"No, clearly not. I never thought of it in that light."</p> + +<p>"Perhaps," suggested Mr. Allgood, "the rule does not apply to +liquids."</p> + +<p>"Just what I was thinking, Allgood. It would seem that we must make an +exception in the case of liquids."</p> + +<p>"But it would be awkward," said George, with a smile, "if we also had +to except the case of solids. For instance, let us take the solid +earth. One mile square equals one square mile. Therefore two miles +square must equal two square miles. Is this so?"</p> + +<p>"Well, let me see! No, of course not," Mr. Filkins replied, "because +two miles square is four square miles."</p> + +<p>"Then," said George, "if the axiom is not true in these cases, when is +it true?"</p> + +<p>Mr. Filkins promised to look into the matter, and perhaps the reader +will also like to give it consideration at leisure.</p> + +<p>"Look here, George," said his cousin Reginald Woolley: "by what +fractional part does four-fourths exceed three-fourths?"</p> + +<p>"By one-fourth!" shouted everybody at once.</p> + +<p>"Try another one," George suggested.</p> + +<p>"With pleasure, when you have answered that one correctly," was +Reginald's reply.</p> + +<p>"Do you mean to say that it isn't one-fourth?"</p> + +<p>"Certainly I do."</p> + +<p>Several members of the company failed to see that the correct answer +is "one-third," although Reginald tried to explain that three of +anything, if increased by one-third, becomes four.</p> + +<p>"Uncle John, how do you pronounce 't-o-o'?" asked Willie.</p> + +<p>"'Too," my boy."</p> + +<p>"And how do you pronounce 't-w-o'?"</p> + +<p>"That is also 'too.'"</p> + +<p><span class='pagenum'>Pg 139<a name="Page_139" id="Page_139"></a></span>"Then how do you pronounce the second day of the week?"</p> + +<p>"Well, that I should pronounce 'Tuesday,' not 'Toosday.'"</p> + +<p>"Would you really? I should pronounce it 'Monday.'"</p> + +<p>"If you go on like this, Willie," said Uncle John, with mock severity, +"you will soon be without a friend in the world."</p> + +<p>"Can any of you write down quickly in figures 'twelve thousand twelve +hundred and twelve pounds'?" asked Mr. Allgood.</p> + +<p>His eldest daughter, Miss Mildred, was the only person who happened to +have a pencil at hand.</p> + +<p>"It can't be done," she declared, after making an attempt on the white +table-cloth; but Mr. Allgood showed her that it should be written, +"£13,212."</p> + +<p>"Now it is my turn," said Mildred. "I have been waiting to ask you all +a question. In the Massacre of the Innocents under Herod, a number of +poor little children were buried in the sand with only their feet +sticking out. How might you distinguish the boys from the girls?"</p> + +<p>"I suppose," said Mrs. Allgood, "it is a conundrum—something to do +with their poor little 'souls.'"</p> + +<p>But after everybody had given it up, Mildred reminded the company that +only boys were put to death.</p> + +<p>"Once upon a time," began George, "Achilles had a race with a +tortoise—"</p> + +<p>"Stop, George!" interposed Mr. Allgood. "We won't have that one. I +knew two men in my youth who were once the best of friends, but they +quarrelled over that infernal thing of Zeno's, and they never spoke to +one another again for the rest of their lives. I draw the line at +that, and the other stupid thing by Zeno about the flying arrow. I +don't believe anybody understands them, because I could never do so +myself."</p> + +<p>"Oh, very well, then, father. Here is another. The Post-Office people +were about to erect a line of telegraph-posts over a high hill from +Turmitville to Wurzleton; but as it was found that a railway company +was making a deep level cutting in the same direction, they arranged +to put up the posts beside the line. Now, the posts were to be a +hundred yards apart, the length of the road over the hill being five +miles, and the length of the level cutting only four and a half miles. +How many posts did they save by erecting them on the level?"</p> + +<p>"That is a very simple matter of calculation," said Mr. Filkins. +"Find how many times one hundred yards will go in five miles, and how +many times in four and a half miles. Then deduct one from the other, +and you have the number of posts saved by the shorter route."</p> + +<p>"Quite right," confirmed Mr. Allgood. "Nothing could be easier."</p> + +<p>"That is just what the Post-Office people said," replied George, "but +it is quite wrong. If you look at this sketch that I have just made, +you will see that there is no difference whatever. If the posts are a +hundred yards apart, just the same number will be required on the +level as over the surface of the hill."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/pdoxprty.png" width="400" height="106" alt="" title="" /> +</div> + +<p>"Surely you must be wrong, George," said Mrs. Allgood, "for if the +posts are a hundred yards apart and it is half a mile farther over the +hill, you have to put up posts on that extra half-mile."</p> + +<p>"Look at the diagram, mother. You will see that the distance from post +to post is not the distance from base to base measured along the +ground. I am just the same distance from you if I stand on this spot +on the carpet or stand immediately above it on the chair."</p> + +<p>But Mrs. Allgood was not convinced.</p> + +<p>Mr. Smoothly, the curate, at the end of the table, said at this point +that he had a little question to ask.</p> + +<p>"Suppose the earth were a perfect sphere with a smooth surface, and a +girdle of steel were placed round the Equator so that it touched at +every point."</p> + +<p>"'I'll put a girdle round about the earth in forty minutes,'" muttered +George, quoting the words of Puck in <i>A Midsummer Night's Dream</i>.</p> + +<p>"Now, if six yards were added to the length of the girdle, what would +then be the distance between the girdle and the earth, supposing that +distance to be equal all round?"</p> + +<p>"In such a great length," said Mr. Allgood, "I do not suppose the +distance would be worth mentioning."</p> + +<p>"What do you say, George?" asked Mr. Smoothly.</p> + +<p>"Well, without calculating I should imagine it would be a very minute +fraction of an inch."</p> + +<p>Reginald and Mr. Filkins were of the same opinion.</p> + +<p>"I think it will surprise you all," said the curate, "to learn that +those extra six yards would make the distance from the earth all round +the girdle very nearly a yard!"</p> + +<p>"Very nearly a yard!" everybody exclaimed, with astonishment; but Mr. +Smoothly was quite correct. The increase is independent of the +original length of the girdle, which may be round the earth or round +an orange; in any case the additional six yards will give a distance +of nearly a yard all round. This is apt to surprise the +non-mathematical mind.</p> + +<p>"Did you hear the story of the extraordinary precocity of Mrs. +Perkins's baby that died last week?" asked Mrs. Allgood. "It was only +three months old, and lying at the point of death, when the +grief-stricken mother asked the doctor if nothing could save it. +'Absolutely nothing!' said the doctor. Then the infant looked up +pitifully into its mother's face and said—absolutely nothing!"</p> + +<p>"Impossible!" insisted Mildred. "And only three months old!"</p> + +<p><span class='pagenum'>Pg 140<a name="Page_140" id="Page_140"></a></span>"There have been extraordinary cases of infantile precocity," said +Mr. Filkins, "the truth of which has often been carefully attested. +But are you sure this really happened, Mrs. Allgood?"</p> + +<p>"Positive," replied the lady. "But do you really think it astonishing +that a child of three months should say absolutely nothing? What would +you expect it to say?"</p> + +<p>"Speaking of death," said Mr. Smoothly, solemnly, "I knew two men, +father and son, who died in the same battle during the South African +War. They were both named Andrew Johnson and buried side by side, but +there was some difficulty in distinguishing them on the headstones. +What would you have done?"</p> + +<p>"Quite simple," said Mr. Allgood. "They should have described one as +'Andrew Johnson, Senior,' and the other as 'Andrew Johnson, Junior.'"</p> + +<p>"But I forgot to tell you that the father died first."</p> + +<p>"What difference can that make?"</p> + +<p>"Well, you see, they wanted to be absolutely exact, and that was the +difficulty."</p> + +<p>"But I don't see any difficulty," said Mr. Allgood, nor could anybody +else.</p> + +<p>"Well," explained Mr. Smoothly, "it is like this. If the father died +first, the son was then no longer 'Junior.' Is that so?"</p> + +<p>"To be strictly exact, yes."</p> + +<p>"That is just what they wanted—to be strictly exact. Now, if he was +no longer 'Junior,' then he did not die 'Junior." Consequently it must +be incorrect so to describe him on the headstone. Do you see the +point?"</p> + +<p>"Here is a rather curious thing," said Mr. Filkins, "that I have just +remembered. A man wrote to me the other day that he had recently +discovered two old coins while digging in his garden. One was dated +'51 B.C.,' and the other one marked 'George I.' How do I know that he +was not writing the truth?"</p> + +<p>"Perhaps you know the man to be addicted to lying," said Reginald.</p> + +<p>"But that would be no proof that he was not telling the truth in this +instance."</p> + +<p>"Perhaps," suggested Mildred, "you know that there were no coins made +at those dates.</p> + +<p>"On the contrary, they were made at both periods."</p> + +<p>"Were they silver or copper coins?" asked Willie.</p> + +<p>"My friend did not state, and I really cannot see, Willie, that it +makes any difference."</p> + +<p>"I see it!" shouted Reginald. "The letters 'B.C.' would never be used +on a coin made before the birth of Christ. They never anticipated the +event in that way. The letters were only adopted later to denote dates +previous to those which we call 'A.D.' That is very good; but I cannot +see why the other statement could not be correct."</p> + +<p>"Reginald is quite right," said Mr. Filkins, "about the first coin. +The second one could not exist, because the first George would never +be described in his lifetime as 'George I.'"</p> + +<p>"Why not?" asked Mrs. Allgood. "He <i>was</i> George I."</p> + +<p>"Yes; but they would not know it until there was a George II."</p> + +<p>"Then there was no George II. until George III. came to the throne?"</p> + +<p>"That does not follow. The second George becomes 'George II.' on +account of there having been a 'George I.'"</p> + +<p>"Then the first George was 'George I.' on account of there having been +no king of that name before him."</p> + +<p>"Don't you see, mother," said George Allgood, "we did not call Queen +Victoria 'Victoria I.;' but if there is ever a 'Victoria II.,' then +she will be known that way."</p> + +<p>"But there <i>have</i> been several Georges, and therefore he was 'George +I.' There <i>haven't</i> been several Victorias, so the two cases are not +similar."</p> + +<p>They gave up the attempt to convince Mrs. Allgood, but the reader +will, of course, see the point clearly.</p> + +<p>"Here is a question," said Mildred Allgood, "that I should like some +of you to settle for me. I am accustomed to buy from our greengrocer +bundles of asparagus, each 12 inches in circumference. I always put a +tape measure round them to make sure I am getting the full quantity. +The other day the man had no large bundles in stock, but handed me +instead two small ones, each 6 inches in circumference. 'That is the +same thing,' I said, 'and, of course, the price will be the same;' but +he insisted that the two bundles together contained more than the +large one, and charged me a few pence extra. Now, what I want to know +is, which of us was correct? Would the two small bundles contain the +same quantity as the large one? Or would they contain more?"</p> + +<p>"That is the ancient puzzle," said Reginald, laughing, "of the sack of +corn that Sempronius borrowed from Caius, which your greengrocer, +perhaps, had been reading about somewhere. He caught you beautifully."</p> + +<p>"Then they were equal?"</p> + +<p>"On the contrary, you were both wrong, and you were badly cheated. You +only got half the quantity that would have been contained in a large +bundle, and therefore ought to have been charged half the original +price, instead of more."</p> + +<p>Yes, it was a bad swindle, undoubtedly. A circle with a circumference +half that of another must have its area a quarter that of the other. +Therefore the two small bundles contained together only half as much +asparagus as a large one.</p> + +<p>"Mr. Filkins, can you answer this?" asked Willie. "There is a man in +the next village who eats two eggs for breakfast every morning."</p> + +<p>"Nothing very extraordinary in that," George broke in. "If you told us +that the two eggs ate the man it would be interesting."</p> + +<p>"Don't interrupt the boy, George," said his mother.</p> + +<p>"Well," Willie continued, "this man neither buys, borrows, barters, +begs, steals, nor finds the eggs. He doesn't keep hens, and the eggs +<span class='pagenum'>Pg 141<a name="Page_141" id="Page_141"></a></span>are not given to him. How does he get the eggs?"</p> + +<p>"Does he take them in exchange for something else?" asked Mildred.</p> + +<p>"That would be bartering them," Willie replied.</p> + +<p>"Perhaps some friend sends them to him," suggested Mrs. Allgood.</p> + +<p>"I said that they were not given to him."</p> + +<p>"I know," said George, with confidence. "A strange hen comes into his +place and lays them."</p> + +<p>"But that would be finding them, wouldn't it?"</p> + +<p>"Does he hire them?" asked Reginald.</p> + +<p>"If so, he could not return them after they were eaten, so that would +be stealing them."</p> + +<p>"Perhaps it is a pun on the word 'lay,'" Mr. Filkins said. "Does he +lay them on the table?"</p> + +<p>"He would have to get them first, wouldn't he? The question was, How +does he get them?"</p> + +<p>"Give it up!" said everybody. Then little Willie crept round to the +protection of his mother, for George was apt to be rough on such +occasions.</p> + +<p>"The man keeps ducks!" he cried, "and his servant collects the eggs +every morning."</p> + +<p>"But you said he doesn't keep birds!" George protested.</p> + +<p>"I didn't, did I, Mr. Filkins? I said he doesn't keep hens."</p> + +<p>"But he finds them," said Reginald.</p> + +<p>"No; I said his servant finds them."</p> + +<p>"Well, then," Mildred interposed, "his servant gives them to him."</p> + +<p>"You cannot give a man his own property, can you?"</p> + +<p>All agreed that Willie's answer was quite satisfactory. Then Uncle +John produced a little fallacy that "brought the proceedings to a +close," as the newspapers say.</p> + +<hr style="width: 30%;" /> +<p><a name="X_413_A_CHESSBOARD_FALLACY" id="X_413_A_CHESSBOARD_FALLACY"></a><a href="#X_413_A_CHESSBOARD_FALLACYa"><b>413.—A CHESSBOARD FALLACY.</b></a></p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/q413.png" width="500" height="286" alt="" title="" /> +</div> + +<p>"Here is a diagram of a chessboard," he said. "You see there are +sixty-four squares—eight by eight. Now I draw a straight line from +the top left-hand corner, where the first and second squares meet, to +the bottom right-hand corner. I cut along this line with the scissors, +slide up the piece that I have marked B, and then clip off the little +corner C by a cut along the first upright line. This little piece will +exactly fit into its place at the top, and we now have an oblong with +seven squares on one side and nine squares on the other. There are, +therefore, now only sixty-three squares, because seven multiplied by +nine makes sixty-three. Where on earth does that lost square go to? I +have tried over and over again to catch the little beggar, but he +always eludes me. For the life of me I cannot discover where he hides +himself."</p> + +<p>"It seems to be like the other old chessboard fallacy, and perhaps the +explanation is the same," said Reginald—"that the pieces do not +exactly fit."</p> + +<p>"But they <i>do</i> fit," said Uncle John. "Try it, and you will see."</p> + +<p>Later in the evening Reginald and George, were seen in a corner with +their heads together, trying to catch that elusive little square, and +it is only fair to record that before they retired for the night they +succeeded in securing their prey, though some others of the company +failed to see it when captured. Can the reader solve the little +mystery?</p> + + + +<hr style="width: 65%;" /><p><span class='pagenum'>Pg 142<a name="Page_142" id="Page_142"></a></span></p> +<h2><a name="UNCLASSIFIED_PROBLEMS" id="UNCLASSIFIED_PROBLEMS"></a><a href="#CONTENTS">UNCLASSIFIED PROBLEMS.</a></h2> + + +<p class='center'> +"A snapper up of unconsidered trifles."<br /> +<span style="margin-left: 8em;"><i>Winter's Tale</i>, iv. 2.</span><br /> +</p> + +<hr style="width: 30%;" /> +<p><a name="X_414_WHO_WAS_FIRST" id="X_414_WHO_WAS_FIRST"></a><a href="#X_414_WHO_WAS_FIRSTa"><b>414.—WHO WAS FIRST?</b></a></p> + +<p>Anderson, Biggs, and Carpenter were staying together at a place by the +seaside. One day they went out in a boat and were a mile at sea when a +rifle was fired on shore in their direction. Why or by whom the shot +was fired fortunately does not concern us, as no information on these +points is obtainable, but from the facts I picked up we can get +material for a curious little puzzle for the novice.</p> + +<p>It seems that Anderson only heard the report of the gun, Biggs only +saw the smoke, and Carpenter merely saw the bullet strike the water +near them. Now, the question arises: Which of them first knew of the +discharge of the rifle?</p> + +<hr style="width: 30%;" /> +<p><a name="X_415_A_WONDERFUL_VILLAGE" id="X_415_A_WONDERFUL_VILLAGE"></a><a href="#X_415_A_WONDERFUL_VILLAGEa"><b>415.—A WONDERFUL VILLAGE.</b></a></p> + +<p>There is a certain village in Japan, situated in a very low valley, +and yet the sun is nearer to the inhabitants every noon, by 3,000 +miles and upwards, than when he either rises or sets to these people. +In what part of the country is the village situated?</p> + +<hr style="width: 30%;" /> +<p><a name="X_416_A_CALENDAR_PUZZLE" id="X_416_A_CALENDAR_PUZZLE"></a><a href="#X_416_A_CALENDAR_PUZZLEa"><b>416.—A CALENDAR PUZZLE.</b></a></p> + +<p>If the end of the world should come on the first day of a new century, +can you say what are the chances that it will happen on a Sunday?</p> + +<hr style="width: 30%;" /> +<p><a name="X_417_THE_TIRING_IRONS" id="X_417_THE_TIRING_IRONS"></a><a href="#X_417_THE_TIRING_IRONSa"><b>417.—THE TIRING IRONS.</b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q417a.png" width="600" height="174" alt="" title="" /> +</div> + +<p>The illustration represents one of the most ancient of all mechanical +puzzles. Its origin is unknown. Cardan, the mathematician, wrote about +it in 1550, and Wallis in 1693; while it is said still to be found in +obscure English villages (sometimes deposited in strange places, such +as a church belfry), made of iron, and appropriately called +"tiring-irons," and to be used by the Norwegians to-day as a lock for +boxes and bags. In the toyshops it is sometimes called the "Chinese +rings," though there seems to be no authority for the description, and +it more frequently goes by the unsatisfactory name of "the puzzling +rings." The French call it "Baguenaudier."</p> + +<p>The puzzle will be seen to consist of a simple <i>loop</i> of wire fixed in +a handle to be held in the left hand, and a certain number of <i>rings</i> +secured by <i>wires</i> which pass through holes in the <i>bar</i> and are kept +there by their blunted ends. The wires work freely in the bar, but +cannot come apart from it, nor can the wires be removed from the +rings. The general puzzle is to detach the loop completely from all +the rings, and then to put them all on again.</p> + +<p>Now, it will be seen at a glance that the first ring (to the right) +can be taken off at any time by sliding it over the end and dropping +it through the loop; or it may be put on by reversing the operation. +With this exception, the only ring that can ever be removed is the one +that happens to be a contiguous second on the loop at the right-hand +end. Thus, with all the rings on, the second can be dropped at once; +with the first ring down, you cannot drop the second, but may remove +the third; with the first three rings down, you cannot drop the +fourth, but may remove the fifth; and so on. It will be found that the +first and second rings can be dropped together or put on together; but +to prevent confusion we will throughout disallow this exceptional +double move, and say that only one ring may be put on or removed at a +time.</p> + +<p>We can thus take off one ring in 1 move; two rings in 2 moves; three +rings in 5 moves; four rings in 10 moves; five rings in 21 moves; and +if we keep on doubling (and adding one where the number of rings is +odd) we may easily ascertain the number of moves for completely +removing any number of rings. To get off all the seven rings requires +85 moves. Let us look at the five moves made in removing the first +three rings, the circles above the line standing for rings on the loop +and those under for rings off the loop.</p> + +<p>Drop the first ring; drop the third; put up the first; drop the +second; and drop the first—5 moves, as shown clearly in the diagrams. +The dark circles show at each stage, from the starting position to the +finish, which rings it is possible to drop. After move 2 it will be +noticed that no ring can be dropped until one has been put on, because +the first and second rings from the right now on the loop are not +together. After the fifth move, if we wish to remove all seven <span class='pagenum'>Pg 143<a name="Page_143" id="Page_143"></a></span>rings +we must now drop the fifth. But before we can then remove the fourth +it is necessary to put on the first three and remove the first two. We +shall then have 7, 6, 4, 3 on the loop, and may therefore drop the +fourth. When we have put on 2 and 1 and removed 3, 2, 1, we may drop +the seventh ring. The next operation then will be to get 6, 5, 4, 3, +2, 1 on the loop and remove 4, 3, 2, 1, when 6 will come off; then get +5, 4, 3, 2, 1 on the loop, and remove 3, 2, 1, when 5 will come off; +then get 4, 3, 2, 1 on the loop and remove 2, 1, when 4 will come off; +then get 3, 2, 1 on the loop and remove 1, when 3 will come off; then +get 2, 1 on the loop, when 2 will come off; and 1 will fall through on +the 85th move, leaving the loop quite free. The reader should now be +able to understand the puzzle, whether or not he has it in his hand in +a practical form.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q417b.png" width="400" height="755" alt="" title="" /> +</div> + +<p>The particular problem I propose is simply this. Suppose there are +altogether fourteen rings on the tiring-irons, and we proceed to take +them all off in the correct way so as not to waste any moves. What +will be the position of the rings after the 9,999th move has been +made?</p> + +<hr style="width: 30%;" /> +<p><a name="X_418_SUCH_A_GETTING_UPSTAIRS" id="X_418_SUCH_A_GETTING_UPSTAIRS"></a><a href="#X_418_SUCH_A_GETTING_UPSTAIRSa"><b>418.—SUCH A GETTING UPSTAIRS.</b></a></p> + +<p>In a suburban villa there is a small staircase with eight steps, not +counting the landing. The little puzzle with which Tommy Smart +perplexed his family is this. You are required to start from the +bottom and land twice on the floor above (stopping there at the +finish), having returned once to the ground floor. But you must be +careful to use every tread the same number of times. In how few steps +can you make the ascent? It seems a very simple matter, but it is more +than likely that at your first attempt you will make a great many more +steps than are necessary. Of course you must not go more than one +riser at a time.</p> + +<p>Tommy knows the trick, and has shown it to his father, who professes +to have a contempt for such things; but when the children are in bed +the pater will often take friends out into the hall and enjoy a good +laugh at their bewilderment. And yet it is all so very simple when you +know how it is done.</p> + +<hr style="width: 30%;" /> +<p><a name="X_419_THE_FIVE_PENNIES" id="X_419_THE_FIVE_PENNIES"></a><a href="#X_419_THE_FIVE_PENNIESa"><b>419.—THE FIVE PENNIES.</b></a></p> + +<p>Here is a really hard puzzle, and yet its conditions are so absurdly +simple. Every reader knows how to place four pennies so that they are +equidistant from each other. All you have to do is to arrange three of +them flat on the table so that they touch one another in the form of a +triangle, and lay the fourth penny on top in the centre. Then, as +every penny touches every other penny, they are all at equal distances +from one another. Now try to do the same thing with five +pennies—place them so that every penny shall touch every other +penny—and you will find it a different matter altogether.</p> + +<hr style="width: 30%;" /> +<p><a name="X_420_THE_INDUSTRIOUS_BOOKWORM" id="X_420_THE_INDUSTRIOUS_BOOKWORM"></a><a href="#X_420_THE_INDUSTRIOUS_BOOKWORMa"><b>420.—THE INDUSTRIOUS BOOKWORM.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q420.png" width="400" height="441" alt="" title="" /> +</div> + +<p>Our friend Professor Rackbrane is seen in the illustration to be +propounding another of his <span class='pagenum'>Pg 144<a name="Page_144" id="Page_144"></a></span>little posers. He is explaining that since +he last had occasion to take down those three volumes of a learned +book from their place on his shelves a bookworm has actually bored a +hole straight through from the first page to the last. He says that +the leaves are together three inches thick in each volume, and that +every cover is exactly one-eighth of an inch thick, and he asks how +long a tunnel had the industrious worm to bore in preparing his new +tube railway. Can you tell him?</p> + +<hr style="width: 30%;" /> +<p><a name="X_421_A_CHAIN_PUZZLE" id="X_421_A_CHAIN_PUZZLE"></a><a href="#X_421_A_CHAIN_PUZZLEa"><b>421.—A CHAIN PUZZLE.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q421.png" width="400" height="335" alt="" title="" /> +</div> + +<p>This is a puzzle based on a pretty little idea first dealt with by the +late Mr. Sam Loyd. A man had nine pieces of chain, as shown in the +illustration. He wanted to join these fifty links into one endless +chain. It will cost a penny to open any link and twopence to weld a +link together again, but he could buy a new endless chain of the same +character and quality for 2<i>s</i>. 2<i>d</i>. What was the cheapest course for him +to adopt? Unless the reader is cunning he may find himself a good way +out in his answer.</p> + +<hr style="width: 30%;" /> +<p><a name="X_422_THE_SABBATH_PUZZLE" id="X_422_THE_SABBATH_PUZZLE"></a><a href="#X_422_THE_SABBATH_PUZZLEa"><b>422.—THE SABBATH PUZZLE.</b></a></p> + +<p>I have come across the following little poser in an old book. I wonder +how many readers will see the author's intended solution to the +riddle.</p> + +<p> +<span style="margin-left: 2em;">Christians the week's <i>first</i> day for Sabbath hold;</span><br /> +<span style="margin-left: 2em;">The Jews the <i>seventh</i>, as they did of old;</span><br /> +<span style="margin-left: 2em;">The Turks the <i>sixth</i>, as we have oft been told.</span><br /> +<span style="margin-left: 2em;">How can these three, in the same place and day,</span><br /> +<span style="margin-left: 2em;">Have each his own true Sabbath? tell, I pray.</span><br /> +</p> + +<hr style="width: 30%;" /> +<p><a name="X_423_THE_RUBY_BROOCH" id="X_423_THE_RUBY_BROOCH"></a><a href="#X_423_THE_RUBY_BROOCHa"><b>423.—THE RUBY BROOCH.</b></a></p> + +<p>The annals of Scotland Yard contain some remarkable cases of jewel +robberies, but one of the most perplexing was the theft of Lady +Littlewood's rubies. There have, of course, been many greater +robberies in point of value, but few so artfully conceived. Lady +Littlewood, of Romley Manor, had a beautiful but rather eccentric +heirloom in the form of a ruby brooch. While staying at her town house +early in the eighties she took the jewel to a shop in Brompton for +some slight repairs.</p> + +<p>"A fine collection of rubies, madam," said the shopkeeper, to whom her +ladyship was a stranger.</p> + +<p>"Yes," she replied; "but curiously enough I have never actually +counted them. My mother once pointed out to me that if you start from +the centre and count up one line, along the outside and down the next +line, there are always eight rubies. So I should always know if a +stone were missing."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q423.png" width="400" height="400" alt="" title="" /> +</div> + +<p>Six months later a brother of Lady Little<span class='pagenum'>Pg 145<a name="Page_145" id="Page_145"></a></span>wood's, who had returned +from his regiment in India, noticed that his sister was wearing the +ruby brooch one night at a county ball, and on their return home asked +to look at it more closely. He immediately detected the fact that four +of the stones were gone.</p> + +<p>"How can that possibly be?" said Lady Littlewood. "If you count up one +line from the centre, along the edge, and down the next line, in any +direction, there are always eight stones. This was always so and is so +now. How, therefore, would it be possible to remove a stone without my +detecting it?"</p> + +<p>"Nothing could be simpler," replied the brother. "I know the brooch +well. It originally contained forty-five stones, and there are now +only forty-one. Somebody has stolen four rubies, and then reset as +small a number of the others as possible in such a way that there +shall always be eight in any of the directions you have mentioned."</p> + +<p>There was not the slightest doubt that the Brompton jeweller was the +thief, and the matter was placed in the hands of the police. But the +man was wanted for other robberies, and had left the neighbourhood +some time before. To this day he has never been found.</p> + +<p>The interesting little point that at first baffled the police, and +which forms the subject of our puzzle, is this: How were the +forty-five rubies originally arranged on the brooch? The illustration +shows exactly how the forty-one were arranged after it came back from +the jeweller; but although they count eight correctly in any of the +directions mentioned, there are four stones missing.</p> + +<hr style="width: 30%;" /> +<p><a name="X_424_THE_DOVETAILED_BLOCK" id="X_424_THE_DOVETAILED_BLOCK"></a><a href="#X_424_THE_DOVETAILED_BLOCKa"><b>424.—THE DOVETAILED BLOCK.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q424.png" width="400" height="320" alt="" title="" /> +</div> + +<p>Here is a curious mechanical puzzle that was given to me some years +ago, but I cannot say who first invented it. It consists of two solid +blocks of wood securely dovetailed together. On the other two vertical +sides that are not visible the appearance is precisely the same as on +those shown. How were the pieces put together? When I published this +little puzzle in a London newspaper I received (though they were +unsolicited) quite a stack of models, in oak, in teak, in mahogany, +rosewood, satinwood, elm, and deal; some half a foot in length, and +others varying in size right down to a delicate little model about +half an inch square. It seemed to create considerable interest.</p> + +<hr style="width: 30%;" /> +<p><a name="X_425_JACK_AND_THE_BEANSTALK" id="X_425_JACK_AND_THE_BEANSTALK"></a><a href="#X_425_JACK_AND_THE_BEANSTALKa"><b>425.—JACK AND THE BEANSTALK.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q425.png" width="400" height="633" alt="" title="" /> +</div> + +<p>The illustration, by a British artist, is a sketch of Jack climbing +the beanstalk. Now, the artist has made a serious blunder in this +drawing. Can you find out what it is?</p> + +<hr style="width: 30%;" /> +<p><a name="X_426_THE_HYMN-BOARD_POSER" id="X_426_THE_HYMN-BOARD_POSER"></a><a href="#X_426_THE_HYMN-BOARD_POSERa"><b>426.—THE HYMN-BOARD POSER.</b></a></p> + +<p>The worthy vicar of Chumpley St. Winifred is in great distress. A +little church difficulty has arisen that all the combined intelligence +of the parish seems unable to surmount. What this difficulty is I will +state hereafter, but it may add to the interest of the problem if I +first give a short account of the curious position that has been +brought about. It all has to do with the church hymn-boards, the +plates of which have become so damaged that they have ceased to fulfil +the purpose for which they were devised. A generous parishioner has +promised to pay for a new set of plates at a certain rate of cost; but +strange as it may seem, no agreement can be come to as to what that +cost should be. The proposed maker of the plates has named <span class='pagenum'>Pg 146<a name="Page_146" id="Page_146"></a></span>a price +which the donor declares to be absurd. The good vicar thinks they are +both wrong, so he asks the schoolmaster to work out the little sum. +But this individual declares that he can find no rule bearing on the +subject in any of his arithmetic books. An application having been +made to the local medical practitioner, as a man of more than average +intellect at Chumpley, he has assured the vicar that his practice is +so heavy that he has not had time even to look at it, though his +assistant whispers that the doctor has been sitting up unusually late +for several nights past. Widow Wilson has a smart son, who is reputed +to have once won a prize for puzzle-solving. He asserts that as he +cannot find any solution to the problem it must have something to do +with the squaring of the circle, the duplication of the cube, or the +trisection of an angle; at any rate, he has never before seen a puzzle +on the principle, and he gives it up.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q426.png" width="400" height="523" alt="" title="" /> +</div> + +<p>This was the state of affairs when the assistant curate (who, I should +say, had frankly confessed from the first that a profound study of +theology had knocked out of his head all the knowledge of mathematics +he ever possessed) kindly sent me the puzzle.</p> + +<p>A church has three hymn-boards, each to indicate the numbers of five +different hymns to be sung at a service. All the boards are in use at +the same service. The hymn-book contains 700 hymns. A new set of +numbers is required, and a kind parishioner offers to present a set +painted on metal plates, but stipulates that only the smallest number +of plates necessary shall be purchased. The cost of each plate is to +be 6<i>d</i>., and for the painting of each plate the charges are to be: For +one plate, 1<i>s</i>.; for two plates alike, 11¾<i>d</i>. each; for three plates +alike, 11½<i>d</i>. each, and so on, the charge being one farthing less +per plate for each similarly painted plate. Now, what should be the +lowest cost?</p> + +<p>Readers will note that they are required to use every legitimate and +practical method of economy. The illustration will make clear the +nature of the three hymn-boards and plates. The five hymns are here +indicated by means of twelve plates. These plates slide in separately +at the back, and in the illustration there is room, of course, for +three more plates.</p> + +<hr style="width: 30%;" /> +<p><a name="X_427_PHEASANT-SHOOTING" id="X_427_PHEASANT-SHOOTING"></a><a href="#X_427_PHEASANT-SHOOTINGa"><b>427.—PHEASANT-SHOOTING.</b></a></p> + +<p>A Cockney friend, who is very apt to draw the long bow, and is +evidently less of a sportsman than he pretends to be, relates to me +the following not very credible yarn:—</p> + +<p>"I've just been pheasant-shooting with my friend the duke. We had +splendid sport, and I made some wonderful shots. What do you think of +this, for instance? Perhaps you can twist it into a puzzle. The duke +and I were crossing a field when suddenly twenty-four pheasants rose +on the wing right in front of us. I fired, and two-thirds of them +dropped dead at my feet. Then the duke had a shot at what were left, +and brought down three-twenty-fourths of them, wounded in the wing. +Now, out of those twenty-four birds, how many still remained?"</p> + +<p>It seems a simple enough question, but can the reader give a correct +answer?</p> + +<hr style="width: 30%;" /> +<p><a name="X_428_THE_GARDENER_AND_THE_COOK" id="X_428_THE_GARDENER_AND_THE_COOK"></a><a href="#X_428_THE_GARDENER_AND_THE_COOKa"><b>428.—THE GARDENER AND THE COOK.</b></a></p> + +<p>A correspondent, signing himself "Simple Simon," suggested that I +should give a special catch puzzle in the issue of <i>The Weekly +Dispatch</i> for All Fools' Day, 1900. So I gave the following, and it +caused considerable amusement; for out of a very large body of +competitors, many quite expert, not a single person solved it, though +it ran for nearly a month.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q428.png" width="400" height="365" alt="" title="" /> +</div> + +<p>"The illustration is a fancy sketch of my correspondent, 'Simple +Simon,' in the act of trying to solve the following innocent little +<span class='pagenum'>Pg 147<a name="Page_147" id="Page_147"></a></span>arithmetical puzzle. A race between a man and a woman that I happened +to witness one All Fools' Day has fixed itself indelibly on my memory. +It happened at a country-house, where the gardener and the cook +decided to run a race to a point 100 feet straight away and return. I +found that the gardener ran 3 feet at every bound and the cook only 2 +feet, but then she made three bounds to his two. Now, what was the +result of the race?"</p> + +<p>A fortnight after publication I added the following note: "It has been +suggested that perhaps there is a catch in the 'return,' but there is +not. The race is to a point 100 feet away and home again—that is, a +distance of 200 feet. One correspondent asks whether they take exactly +the same time in turning, to which I reply that they do. Another seems +to suspect that it is really a conundrum, and that the answer is that +'the result of the race was a (matrimonial) tie.' But I had no such +intention. The puzzle is an arithmetical one, as it purports to be."</p> + +<hr style="width: 30%;" /> +<p><a name="X_429_PLACING_HALFPENNIES" id="X_429_PLACING_HALFPENNIES"></a><a href="#X_429_PLACING_HALFPENNIESa"><b>429.—PLACING HALFPENNIES.</b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/q429.png" width="400" height="261" alt="" title="" /> +</div> + +<p>Here is an interesting little puzzle suggested to me by Mr. W. T. +Whyte. Mark off on a sheet of paper a rectangular space 5 inches by 3 +inches, and then find the greatest number of halfpennies that can be +placed within the enclosure under the following conditions. A +halfpenny is exactly an inch in diameter. Place your first halfpenny +where you like, then place your second coin at exactly the distance of +an inch from the first, the third an inch distance from the second, +and so on. No halfpenny may touch another halfpenny or cross the +boundary. Our illustration will make the matter perfectly clear. No. 2 +coin is an inch from No. 1; No. 3 an inch from No. 2; No. 4 an inch +from No. 3; but after No. 10 is placed we can go no further in this +attempt. Yet several more halfpennies might have been got in. How many +can the reader place?</p> + +<hr style="width: 30%;" /> +<p><a name="X_430_FIND_THE_MANS_WIFE" id="X_430_FIND_THE_MANS_WIFE"></a><a href="#X_430_FIND_THE_MANS_WIFEa"><b>430.—FIND THE MAN'S WIFE.</b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/q430.png" width="600" height="217" alt="" title="" /> +</div> + +<p>One summer day in 1903 I was loitering on the Brighton front, watching +the people strolling about on the beach, when the friend who was with +me suddenly drew my attention to an individual who was standing alone, +and said, "Can you point out that man's wife? They are stopping at the +same hotel as I am, and the lady is one of those in view." After a few +minutes' observation, I was successful in indicating the lady +correctly. My friend was curious to know by what method of reasoning I +had arrived at the result. This was my answer:—</p> + +<p>"We may at once exclude that Sister of Mercy and the girl in the short +frock; also the woman selling oranges. It cannot be the lady in +widows' weeds. It is not the lady in the bath chair, because she is +not staying at your hotel, for I happened to see her come out of a +private house this morning assisted by her maid. The two ladies in red +breakfasted at my hotel this morning, and as they were not wearing +outdoor dress I conclude they are staying there. It therefore rests +between the lady in blue and the one with the green parasol. But the +left hand that holds the parasol is, you see, ungloved and bears no +wedding-ring. Consequently I am driven to the conclusion that the lady +in blue is the man's wife—and you say this is correct."</p> + +<p>Now, as my friend was an artist, and as I thought an amusing puzzle +might be devised on the lines of his question, I asked him to make me +a drawing according to some directions that I gave him, and I have +pleasure in presenting his production to my readers. It will be seen +that the picture shows six men and six ladies: Nos. 1, 3, 5, 7, 9, and +11 are ladies, and Nos. 2, <span class='pagenum'>Pg 148<a name="Page_148" id="Page_148"></a></span>4, 6, 8, 10, and 12 are men. These twelve +individuals represent six married couples, all strangers to one +another, who, in walking aimlessly about, have got mixed up. But we +are only concerned with the man that is wearing a straw hat—Number +10. The puzzle is to find this man's wife. Examine the six ladies +carefully, and see if you can determine which one of them it is.</p> + +<p>I showed the picture at the time to a few friends, and they expressed +very different opinions on the matter. One said, "I don't believe he +would marry a girl like Number 7." Another said, "I am sure a nice +girl like Number 3 would not marry such a fellow!" Another said, "It +must be Number 1, because she has got as far away as possible from the +brute!" It was suggested, again, that it must be Number 11, because +"he seems to be looking towards her;" but a cynic retorted, "For that +very reason, if he is really looking at her, I should say that she is +not his wife!"</p> + +<p>I now leave the question in the hands of my readers. Which is really +Number 10's wife?</p> + +<p>The illustration is of necessity considerably reduced from the large +scale on which it originally appeared in <i>The Weekly Dispatch</i> (24th +May 1903), but it is hoped that the details will be sufficiently clear +to allow the reader to derive entertainment from its examination. In +any case the solution given will enable him to follow the points with +interest.<br /><br /><br /><br /></p> + + + +<hr style="width: 65%;" /> +<h2><a name="SOLUTIONS" id="SOLUTIONS"></a><a href="#CONTENTS">SOLUTIONS.</a><br /><br /><br /></h2> + +<hr style="width: 30%;" /> +<p><a name="X_1_A_POST-OFFICE_PERPLEXITYa" id="X_1_A_POST-OFFICE_PERPLEXITYa"></a><a href="#X_1_A_POST-OFFICE_PERPLEXITY"><b>1.—A POST-OFFICE PERPLEXITY.—<i>solution</i></b></a></p> + +<p>The young lady supplied 5 twopenny stamps, 30 penny stamps, and 8 +twopence-halfpenny stamps, which delivery exactly fulfils the +conditions and represents a cost of five shillings.</p> + +<hr style="width: 30%;" /> +<p><a name="X_2_YOUTHFUL_PRECOCITYa" id="X_2_YOUTHFUL_PRECOCITYa"></a><a href="#X_2_YOUTHFUL_PRECOCITY"><b>2.—YOUTHFUL PRECOCITY.—<i>solution</i></b></a></p> + +<p>The price of the banana must have been one penny farthing. Thus, 960 +bananas would cost £5, and 480 sixpences would buy 2,304 bananas.</p> + +<hr style="width: 30%;" /> +<p><a name="X_3_AT_A_CATTLE_MARKETa" id="X_3_AT_A_CATTLE_MARKETa"></a><a href="#X_3_AT_A_CATTLE_MARKET"><b>3.—AT A CATTLE MARKET.—<i>solution</i></b></a></p> + +<p>Jakes must have taken 7 animals to market, Hodge must have taken 11, +and Durrant must have taken 21. There were thus 39 animals altogether.</p> + +<hr style="width: 30%;" /> +<p><a name="X_4_THE_BEANFEAST_PUZZLEa" id="X_4_THE_BEANFEAST_PUZZLEa"></a><a href="#X_4_THE_BEANFEAST_PUZZLE"><b>4.—THE BEANFEAST PUZZLE.—<i>solution</i></b></a></p> + +<p>The cobblers spent 35<i>s</i>., the tailors spent also 35<i>s</i>., the hatters +spent 42<i>s</i>., and the glovers spent 21<i>s</i>. Thus, they spent altogether +£6,13<i>s</i>., while it will be found that the five cobblers spent as much +as four tailors, twelve tailors as much as nine hatters, and six +hatters as much as eight glovers.</p> + +<hr style="width: 30%;" /> +<p><a name="X_5_A_QUEER_COINCIDENCEa" id="X_5_A_QUEER_COINCIDENCEa"></a><a href="#X_5_A_QUEER_COINCIDENCE"><b>5.—A QUEER COINCIDENCE.—<i>solution</i></b></a></p> + +<p>Puzzles of this class are generally solved in the old books by the +tedious process of "working backwards." But a simple general solution +is as follows: If there are <i>n</i> players, the amount held by every +player at the end will be <i>m</i>(2<sup><i>n</i></sup>), the last winner must have held +<i>m</i>(<i>n</i>+1) at the start, the next <i>m</i>(2<i>n</i>+1), the next <i>m</i>(4<i>n</i>+1), +the next <i>m</i>(8<i>n</i>+1), and so on to the first player, who must have +held <i>m</i>(2<sup><i>n</i>-1</sup><i>n</i>+1).</p> + +<p>Thus, in this case, <i>n</i> = 7, and the amount held by every player at the +end was 2<sup>7</sup> farthings. Therefore <i>m</i> = 1, and G started with 8 +farthings, F with 15, E with 29, D with 57, C with 113, B with 225, +and A with 449 farthings.</p> + +<hr style="width: 30%;" /> +<p><a name="X_6_A_CHARITABLE_BEQUESTa" id="X_6_A_CHARITABLE_BEQUESTa"></a><a href="#X_6_A_CHARITABLE_BEQUEST"><b>6.—A CHARITABLE BEQUEST.—<i>solution</i></b></a></p> + +<p>There are seven different ways in which the money may be distributed: +5 women and 19 men, 10 women and 16 men, 15 women and 13 men, 20 women +and 10 men, 25 women and 7 men, 30 women and 4 men, and 35 women and 1 +man. But the last case must not be counted, because the condition was +that there should be "men," and a single man is not men. Therefore the +answer is six years.</p> + +<hr style="width: 30%;" /> +<p><a name="X_7_THE_WIDOWS_LEGACYa" id="X_7_THE_WIDOWS_LEGACYa"></a><a href="#X_7_THE_WIDOWS_LEGACY"><b>7.—THE WIDOW'S LEGACY.—<i>solution</i></b></a></p> + +<p>The widow's share of the legacy must be £205, 2<i>s</i>. 6<i>d</i>. and <sup>10</sup>/<sub>13</sub> of a +penny.</p> + +<hr style="width: 30%;" /> +<p><a name="X_8_INDISCRIMINATE_CHARITYa" id="X_8_INDISCRIMINATE_CHARITYa"></a><a href="#X_8_INDISCRIMINATE_CHARITY"><b>8.—INDISCRIMINATE CHARITY—<i>solution</i></b></a></p> + +<p>The gentleman must have had 3<i>s</i>. 6<i>d</i>. in his pocket when he set out for +home.</p> + +<hr style="width: 30%;" /> +<p><a name="X_9_THE_TWO_AEROPLANESa" id="X_9_THE_TWO_AEROPLANESa"></a><a href="#X_9_THE_TWO_AEROPLANES"><b>9.—THE TWO AEROPLANES.—<i>solution</i></b></a></p> + +<p>The man must have paid £500 and £750 for the two machines, making +together £1,250; but as he sold them for only £1,200, he lost £50 by +the transaction.</p> + +<hr style="width: 30%;" /> +<p><a name="X_10_BUYING_PRESENTSa" id="X_10_BUYING_PRESENTSa"></a><a href="#X_10_BUYING_PRESENTS"><b>10.—BUYING PRESENTS.—<i>solution</i></b></a></p> + +<p>Jorkins had originally £19, 18<i>s</i>. in his pocket, and spent £9, 19<i>s</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_11_THE_CYCLISTS_FEASTa" id="X_11_THE_CYCLISTS_FEASTa"></a><a href="#X_11_THE_CYCLISTS_FEAST"><b>11.—THE CYCLISTS' FEAST.—<i>solution</i></b></a></p> + +<p>There were ten cyclists at the feast. They should have paid 8<i>s</i>. each; +but, owing to the departure of two persons, the remaining eight would +pay 10<i>s</i>. each.</p> + +<hr style="width: 30%;" /> +<p><a name="X_12_A_QUEER_THING_IN_MONEYa" id="X_12_A_QUEER_THING_IN_MONEYa"></a><a href="#X_12_A_QUEER_THING_IN_MONEY"><b>12.—A QUEER THING IN MONEY.—<i>solution</i></b></a></p> + +<p>The answer is as follows: £44,444, 4<i>s</i>. 4<i>d</i>. = 28, and, reduced to pence, +10,666,612 = 28.</p> + +<p>It is a curious little coincidence that in the answer 10,666,612 the +four central figures indicate the only other answer, £66, 6<i>s</i>. 6<i>d</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_13_A_NEW_MONEY_PUZZLEa" id="X_13_A_NEW_MONEY_PUZZLEa"></a><a href="#X_13_A_NEW_MONEY_PUZZLE"><b>13.—A NEW MONEY PUZZLE.—<i>solution</i></b></a></p> + +<p>The smallest sum of money, in pounds, shillings, pence, and farthings, +containing all the nine digits once, and once only, is £2,567, 18<i>s</i>. +9¾<i>d</i>.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 149<a name="Page_149" id="Page_149"></a></span><a name="X_14_SQUARE_MONEYa" id="X_14_SQUARE_MONEYa"></a><a href="#X_14_SQUARE_MONEY"><b>14.—SQUARE MONEY.—<i>solution</i></b></a></p> + +<p>The answer is 1½<i>d</i>. and 3<i>d</i>. Added together they make 4½<i>d</i>., and +1½<i>d</i>. multiplied by 3 is also 4½<i>d</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_15_POCKET_MONEYa" id="X_15_POCKET_MONEYa"></a><a href="#X_15_POCKET_MONEY"><b>15.—POCKET MONEY.—<i>solution</i></b></a></p> + +<p>The largest possible sum is 15<i>s</i>. 9<i>d</i>., composed of a crown and a +half-crown (or three half-crowns), four florins, and a threepenny +piece.</p> + +<hr style="width: 30%;" /> +<p><a name="X_16_THE_MILLIONAIRES_PERPLEXITYa" id="X_16_THE_MILLIONAIRES_PERPLEXITYa"></a><a href="#X_16_THE_MILLIONAIRES_PERPLEXITY"><b>16.—THE MILLIONAIRE'S PERPLEXITY.—<i>solution</i></b></a></p> + +<p>The answer to this quite easy puzzle may, of course, be readily +obtained by trial, deducting the largest power of 7 that is contained +in one million dollars, then the next largest power from the +remainder, and so on. But the little problem is intended to illustrate +a simple direct method. The answer is given at once by converting +1,000,000 to the septenary scale, and it is on this subject of scales +of notation that I propose to write a few words for the benefit of +those who have never sufficiently considered the matter.</p> + +<p>Our manner of figuring is a sort of perfected arithmetical shorthand, +a system devised to enable us to manipulate numbers as rapidly and +correctly as possible by means of symbols. If we write the number +2,341 to represent two thousand three hundred and forty-one dollars, +we wish to imply 1 dollar, added to four times 10 dollars, added to +three times 100 dollars, added to two times 1,000 dollars. From the +number in the units place on the right, every figure to the left is +understood to represent a multiple of the particular power of 10 that +its position indicates, while a cipher (0) must be inserted where +necessary in order to prevent confusion, for if instead of 207 we +wrote 27 it would be obviously misleading. We thus only require ten +figures, because directly a number exceeds 9 we put a second figure to +the left, directly it exceeds 99 we put a third figure to the left, +and so on. It will be seen that this is a purely arbitrary method. It +is working in the denary (or ten) scale of notation, a system +undoubtedly derived from the fact that our forefathers who devised it +had ten fingers upon which they were accustomed to count, like our +children of to-day. It is unnecessary for us ordinarily to state that +we are using the denary scale, because this is always understood in +the common affairs of life.</p> + +<p>But if a man said that he had 6,553 dollars in the septenary (or +seven) scale of notation, you will find that this is precisely the +same amount as 2,341 in our ordinary denary scale. Instead of using +powers of ten, he uses powers of 7, so that he never needs any figure +higher than 6, and 6,553 really stands for 3, added to five times 7, +added to five times 49, added to six times 343 (in the ordinary +notation), or 2,341. To reverse the operation, and convert 2,341 from +the denary to the septenary scale, we divide it by 7, and get 334 and +remainder 3; divide 334 by 7, and get 47 and remainder 5; and so keep +on dividing by 7 as long as there is anything to divide. The +remainders, read backwards, 6, 5, 5, 3, give us the answer, 6,553.</p> + +<p>Now, as I have said, our puzzle may be solved at once by merely +converting 1,000,000 dollars to the septenary scale. Keep on dividing +this number by 7 until there is nothing more left to divide, and the +remainders will be found to be 11333311 which is 1,000,000 expressed +in the septenary scale. Therefore, 1 gift of 1 dollar, 1 gift of 7 +dollars, 3 gifts of 49 dollars, 3 gifts of 343 dollars, 3 gifts of +2,401 dollars, 3 gifts of 16,807 dollars, 1 gift of 117,649 dollars, +and one substantial gift of 823,543 dollars, satisfactorily solves our +problem. And it is the only possible solution. It is thus seen that no +"trials" are necessary; by converting to the septenary scale of +notation we go direct to the answer.</p> + +<hr style="width: 30%;" /> +<p><a name="X_17_THE_PUZZLING_MONEY_BOXESa" id="X_17_THE_PUZZLING_MONEY_BOXESa"></a><a href="#X_17_THE_PUZZLING_MONEY_BOXES"><b>17.—THE PUZZLING MONEY BOXES.—<i>solution</i></b></a></p> + +<p>The correct answer to this puzzle is as follows: John put into his +money-box two double florins (8<i>s</i>.), William a half-sovereign and a +florin (12<i>s</i>.), Charles a crown (5<i>s</i>.), and Thomas a sovereign (20<i>s</i>.). +There are six coins in all, of a total value of 45<i>s</i>. If John had 2<i>s</i>. +more, William 2<i>s</i>. less, Charles twice as much, and Thomas half as much +as they really possessed, they would each have had exactly 10<i>s</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_18_THE_MARKET_WOMENa" id="X_18_THE_MARKET_WOMENa"></a><a href="#X_18_THE_MARKET_WOMEN"><b>18.—THE MARKET WOMEN.—<i>solution</i></b></a></p> + +<p>The price received was in every case 105 farthings. Therefore the +greatest number of women is eight, as the goods could only be sold at +the following rates: 105 lbs. at 1 farthing, 35 at 3, 21 at 5, 15 at +7, 7 at 15, 5 at 21, 3 at 35, and 1 lb. at 105 farthings.</p> + +<hr style="width: 30%;" /> +<p><a name="X_19_THE_NEW_YEARS_EVE_SUPPERSa" id="X_19_THE_NEW_YEARS_EVE_SUPPERSa"></a><a href="#X_19_THE_NEW_YEARS_EVE_SUPPERS"><b>19.—THE NEW YEAR'S EVE SUPPERS.—<i>solution</i></b></a></p> + +<p>The company present on the occasion must have consisted of seven +pairs, ten single men, and one single lady. Thus, there were +twenty-five persons in all, and at the prices stated they would pay +exactly £5 together.</p> + +<hr style="width: 30%;" /> +<p><a name="X_20_BEEF_AND_SAUSAGESa" id="X_20_BEEF_AND_SAUSAGESa"></a><a href="#X_20_BEEF_AND_SAUSAGES"><b>20.—BEEF AND SAUSAGES.—<i>solution</i></b></a></p> + +<p>The lady bought 48 lbs. of beef at 2<i>s</i>., and the same quantity of +sausages at 1<i>s</i>. 6<i>d</i>., thus spending £8, 8<i>s</i>. Had she bought 42 lbs. of +beef and 56 lbs. of sausages she would have spent £4, 4<i>s</i>. on each, and +have obtained 98 lbs. instead of 96 lbs.—a gain in weight of 2 lbs.</p> + +<hr style="width: 30%;" /> +<p><a name="X_21_A_DEAL_IN_APPLESa" id="X_21_A_DEAL_IN_APPLESa"></a><a href="#X_21_A_DEAL_IN_APPLES"><b>21.—A DEAL IN APPLES.—<i>solution</i></b></a></p> + +<p>I was first offered sixteen apples for my shilling, which would be at +the rate of ninepence a dozen. The two extra apples gave me eighteen +for a shilling, which is at the rate of eightpence a dozen, or one +penny a dozen less than the first price asked.</p> + +<hr style="width: 30%;" /> +<p><a name="X_22_A_DEAL_IN_EGGSa" id="X_22_A_DEAL_IN_EGGSa"></a><a href="#X_22_A_DEAL_IN_EGGS"><b>22.—A DEAL IN EGGS.—<i>solution</i></b></a></p> + +<p>The man must have bought ten eggs at fivepence, ten eggs at one penny, +and eighty eggs <span class='pagenum'>Pg 150<a name="Page_150" id="Page_150"></a></span>at a halfpenny. He would then have one hundred eggs +at a cost of eight shillings and fourpence, and the same number of +eggs of two of the qualities.</p> + +<hr style="width: 30%;" /> +<p><a name="X_23_THE_CHRISTMAS-BOXESa" id="X_23_THE_CHRISTMAS-BOXESa"></a><a href="#X_23_THE_CHRISTMAS-BOXES"><b>23.—THE CHRISTMAS-BOXES.—<i>solution</i></b></a></p> + +<p>The distribution took place "some years ago," when the fourpenny-piece +was in circulation. Nineteen persons must each have received nineteen +pence. There are five different ways in which this sum may have been +paid in silver coins. We need only use two of these ways. Thus if +fourteen men each received four four-penny-pieces and one +threepenny-piece, and five men each received five threepenny-pieces +and one fourpenny-piece, each man would receive nineteen pence, and +there would be exactly one hundred coins of a total value of £1, 10<i>s</i>. +1<i>d</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_24_A_SHOPPING_PERPLEXITYa" id="X_24_A_SHOPPING_PERPLEXITYa"></a><a href="#X_24_A_SHOPPING_PERPLEXITY"><b>24.—A SHOPPING PERPLEXITY.—<i>solution</i></b></a></p> + +<p>The first purchase amounted to 1<i>s</i>. 5¾<i>d</i>., the second to 1<i>s</i>. +11½<i>d</i>., and together they make 3<i>s</i>. 5¼<i>d</i>. Not one of these three +amounts can be paid in fewer than six current coins of the realm.</p> + +<hr style="width: 30%;" /> +<p><a name="X_25_CHINESE_MONEYa" id="X_25_CHINESE_MONEYa"></a><a href="#X_25_CHINESE_MONEY"><b>25.—CHINESE MONEY.—<i>solution</i></b></a></p> + +<p>As a ching-chang is worth twopence and four-fifteenths of a +ching-chang, the remaining eleven-fifteenths of a ching-chang must be +worth twopence. Therefore eleven ching-changs are worth exactly thirty +pence, or half a crown. Now, the exchange must be made with seven +round-holed coins and one square-holed coin. Thus it will be seen that +7 round-holed coins are worth seven-elevenths of 15 ching-changs, and +1 square-holed coin is worth one-eleventh of 16 ching-changs—that is, +77 rounds equal 105 ching-changs and 11 squares equal 16 ching-changs. +Therefore 77 rounds added to 11 squares equal 121 ching-changs; or 7 +rounds and 1 square equal 11 ching-changs, or its equivalent, half a +crown. This is more simple in practice than it looks here.</p> + +<hr style="width: 30%;" /> +<p><a name="X_26_THE_JUNIOR_CLERKS_PUZZLEa" id="X_26_THE_JUNIOR_CLERKS_PUZZLEa"></a><a href="#X_26_THE_JUNIOR_CLERKS_PUZZLE"><b>26.—THE JUNIOR CLERKS' PUZZLE.—<i>solution</i></b></a></p> + +<p>Although Snoggs's <i>reason</i> for wishing to take his rise at £2, 10<i>s</i>. +half-yearly did not concern our puzzle, the <i>fact</i> that he was duping +his employer into paying him more than was intended did concern it. +Many readers will be surprised to find that, although Moggs only +received £350 in five years, the artful Snoggs actually obtained £362, +10<i>s</i>. in the same time. The rest is simplicity itself. It is evident +that if Moggs saved £87, 10<i>s</i>. and Snoggs £181, 5<i>s</i>., the latter would +be saving twice as great a proportion of his salary as the former +(namely, one-half as against one-quarter), and the two sums added +together make £268, 15<i>s</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_27_GIVING_CHANGEa" id="X_27_GIVING_CHANGEa"></a><a href="#X_27_GIVING_CHANGE"><b>27.—GIVING CHANGE.—<i>solution</i></b></a></p> + +<p>The way to help the American tradesman out of his dilemma is this. +Describing the coins by the number of cents that they represent, the +tradesman puts on the counter 50 and 25; the buyer puts down 100, 3, +and 2; the stranger adds his 10, 10, 5, 2, and 1. Now, considering +that the cost of the purchase amounted to 34 cents, it is clear that +out of this pooled money the tradesman has to receive 109, the buyer +71, and the stranger his 28 cents. Therefore it is obvious at a glance +that the 100-piece must go to the tradesman, and it then follows that +the 50-piece must go to the buyer, and then the 25-piece can only go +to the stranger. Another glance will now make it clear that the two +10-cent pieces must go to the buyer, because the tradesman now only +wants 9 and the stranger 3. Then it becomes obvious that the buyer +must take the 1 cent, that the stranger must take the 3 cents, and the +tradesman the 5, 2, and 2. To sum up, the tradesman takes 100, 5, 2, +and 2; the buyer, 50, 10, 10, and 1; the stranger, 25 and 3. It will +be seen that not one of the three persons retains any one of his own +coins.</p> + +<hr style="width: 30%;" /> +<p><a name="X_28_DEFECTIVE_OBSERVATIONa" id="X_28_DEFECTIVE_OBSERVATIONa"></a><a href="#X_28_DEFECTIVE_OBSERVATION"><b>28.—DEFECTIVE OBSERVATION.—<i>solution</i></b></a></p> + +<p>Of course the date on a penny is on the same side as Britannia—the +"tail" side. Six pennies may be laid around another penny, all flat on +the table, so that every one of them touches the central one. The +number of threepenny-pieces that may be laid on the surface of a +half-crown, so that no piece lies on another or overlaps the edge of +the half-crown, is one. A second threepenny-piece will overlap the +edge of the larger coin. Few people guess fewer than three, and many +persons give an absurdly high number.</p> + +<hr style="width: 30%;" /> +<p><a name="X_29_THE_BROKEN_COINSa" id="X_29_THE_BROKEN_COINSa"></a><a href="#X_29_THE_BROKEN_COINS"><b>29.—THE BROKEN COINS.—<i>solution</i></b></a></p> + +<p>If the three broken coins when perfect were worth 253 pence, and are +now in their broken condition worth 240 pence, it should be obvious +that <sup>13</sup>/<sub>253</sub> of the original value has been lost. And as the same +fraction of each coin has been broken away, each coin has lost <sup>13</sup>/<sub>253</sub> +of its original bulk.</p> + +<hr style="width: 30%;" /> +<p><a name="X_30_TWO_QUESTIONS_IN_PROBABILITIESa" id="X_30_TWO_QUESTIONS_IN_PROBABILITIESa"></a><a href="#X_30_TWO_QUESTIONS_IN_PROBABILITIES"><b>30.—TWO QUESTIONS IN PROBABILITIES.—<i>solution</i></b></a></p> + +<p>In tossing with the five pennies all at the same time, it is obvious +that there are 32 different ways in which the coins may fall, because +the first coin may fall in either of two ways, then the second coin +may also fall in either of two ways, and so on. Therefore five 2's +multiplied together make 32. Now, how are these 32 ways made up? Here +they are:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>(<i>a</i>)</td><td align='right'>5</td><td align='left'>heads</td><td align='right'>1</td><td align='left'>way</td></tr> +<tr><td align='center'>(<i>b</i>)</td><td align='right'>5</td><td align='left'>tails</td><td align='right'>1</td><td align='left'>way</td></tr> +<tr><td align='center'>(<i>c</i>)</td><td align='right'>4</td><td align='left'>heads and 1 tail</td><td align='right'>5</td><td align='left'>ways</td></tr> +<tr><td align='center'>(<i>d</i>)</td><td align='right'>4</td><td align='left'>tails and 1 head</td><td align='right'>5</td><td align='left'>ways</td></tr> +<tr><td align='center'>(<i>e</i>)</td><td align='right'>3</td><td align='left'>heads and 2 tails</td><td align='right'>10</td><td align='left'>ways</td></tr> +<tr><td align='center'>(<i>f</i>)</td><td align='right'>3</td><td align='left'>tails and 2 heads</td><td align='right'>10</td><td align='left'>ways</td></tr> +</table></div> + +<p>Now, it will be seen that the only favourable cases are <i>a</i>, <i>b</i>, <i>c</i>, +and <i>d</i>—12 cases. The remaining 20 cases are unfavourable, because +they do <span class='pagenum'>Pg 151<a name="Page_151" id="Page_151"></a></span>not give at least four heads or four tails. Therefore the +chances are only 12 to 20 in your favour, or (which is the same thing) +3 to 5. Put another way, you have only 3 chances out of 8.</p> + +<p>The amount that should be paid for a draw from the bag that contains +three sovereigns and one shilling is 15<i>s</i>. 3<i>d</i>. Many persons will say +that, as one's chances of drawing a sovereign were 3 out of 4, one +should pay three-fourths of a pound, or 15<i>s</i>., overlooking the fact +that one must draw at least a shilling—there being no blanks.</p> + +<hr style="width: 30%;" /> +<p><a name="X_31_DOMESTIC_ECONOMYa" id="X_31_DOMESTIC_ECONOMYa"></a><a href="#X_31_DOMESTIC_ECONOMY"><b>31.—DOMESTIC ECONOMY.—<i>solution</i></b></a></p> + +<p>Without the hint that I gave, my readers would probably have been +unanimous in deciding that Mr. Perkins's income must have been £1,710. +But this is quite wrong. Mrs. Perkins says, "We have spent a third of +his yearly income in rent," etc., etc.—that is, in two years they +have spent an amount in rent, etc., equal to one-third of his yearly +income. Note that she does <i>not</i> say that they have spent <i>each year</i> +this sum, whatever it is, but that <i>during the two years</i> that amount +has been spent. The only possible answer, according to the exact +reading of her words, is, therefore, that his income was £180 per +annum. Thus the amount spent in two years, during which his income has +amounted to £360, will be £60 in rent, etc., £90 in domestic expenses, +£20 in other ways, leaving the balance of £190 in the bank as stated.</p> + +<hr style="width: 30%;" /> +<p><a name="X_32_THE_EXCURSION_TICKET_PUZZLEa" id="X_32_THE_EXCURSION_TICKET_PUZZLEa"></a><a href="#X_32_THE_EXCURSION_TICKET_PUZZLE"><b>32.—THE EXCURSION TICKET PUZZLE.—<i>solution</i></b></a></p> + +<p>Nineteen shillings and ninepence may be paid in 458,908,622 different +ways.</p> + +<p>I do not propose to give my method of solution. Any such explanation +would occupy an amount of space out of proportion to its interest or +value. If I could give within reasonable limits a general solution for +all money payments, I would strain a point to find room; but such a +solution would be extremely complex and cumbersome, and I do not +consider it worth the labour of working out.</p> + +<p>Just to give an idea of what such a solution would involve, I will +merely say that I find that, dealing only with those sums of money +that are multiples of threepence, if we only use bronze coins any sum +can be paid in (<i>n</i>+1)<sup>2</sup> ways where <i>n</i> always represents the number +of pence. If threepenny-pieces are admitted, there are</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' class='bb'>2<i>n</i><sup>3</sup>+15<i>n</i><sup>2</sup>+33<i>n</i></td><td rowspan='2'> + 1 </td></tr> +<tr><td align='center'>18</td></tr> +</table></div> + +<p>ways. If sixpences are also used there are</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' class='bb'><i>n</i><sup>4</sup>+22<i>n</i><sup>3</sup>+159<i>n</i><sup>2</sup>+414<i>n</i>+216</td></tr> +<tr><td align='center'>216</td></tr> +</table></div> + +<p>ways, when the sum is a multiple of sixpence, and the constant, 216, +changes to 324 when the money is not such a multiple. And so the +formulas increase in complexity in an accelerating ratio as we go on +to the other coins.</p> + +<p>I will, however, add an interesting little table of the possible ways +of changing our current coins which I believe has never been given in +a book before. Change may be given for a</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Farthing in</td><td align='left'>0 way.</td></tr> +<tr><td align='left'>Halfpenny in</td><td align='left'>1 way.</td></tr> +<tr><td align='left'>Penny in</td><td align='left'>3 ways.</td></tr> +<tr><td align='left'>Threepenny-piece in</td><td align='left'>16 ways.</td></tr> +<tr><td align='left'>Sixpence in</td><td align='left'>66 ways.</td></tr> +<tr><td align='left'>Shilling in</td><td align='left'>402 ways.</td></tr> +<tr><td align='left'>Florin in</td><td align='left'>3,818 ways.</td></tr> +<tr><td align='left'>Half-crown in</td><td align='left'>8,709 ways.</td></tr> +<tr><td align='left'>Double florin in</td><td align='left'>60,239 ways.</td></tr> +<tr><td align='left'>Crown in</td><td align='left'>166,651 ways.</td></tr> +<tr><td align='left'>Half-sovereign in</td><td align='left'>6,261,622 ways.</td></tr> +<tr><td align='left'>Sovereign in</td><td align='left'>500,291,833 ways.</td></tr> +</table></div> + +<p>It is a little surprising to find that a sovereign may be changed in +over five hundred million different ways. But I have no doubt as to +the correctness of my figures.</p> + +<hr style="width: 30%;" /> +<p><a name="X_33_A_PUZZLE_IN_REVERSALSa" id="X_33_A_PUZZLE_IN_REVERSALSa"></a><a href="#X_33_A_PUZZLE_IN_REVERSALS"><b>33.—A PUZZLE IN REVERSALS.—<i>solution</i></b></a></p> + +<p>(i) £13. (2) £23, 19<i>s</i>. 11<i>d</i>. The words "the number of pounds exceeds +that of the pence" exclude such sums of money as £2, 16<i>s</i>. 2<i>d</i>. and all +sums under £1.</p> + +<hr style="width: 30%;" /> +<p><a name="X_34_THE_GROCER_AND_DRAPERa" id="X_34_THE_GROCER_AND_DRAPERa"></a><a href="#X_34_THE_GROCER_AND_DRAPER"><b>34.—THE GROCER AND DRAPER.—<i>solution</i></b></a></p> + +<p>The grocer was delayed half a minute and the draper eight minutes and +a half (seventeen times as long as the grocer), making together nine +minutes. Now, the grocer took twenty-four minutes to weigh out the +sugar, and, with the half-minute delay, spent 24 min. 30 sec. over the +task; but the draper had only to make <i>forty-seven</i> cuts to divide the +roll of cloth, containing forty-eight yards, into yard pieces! This +took him 15 min. 40 sec., and when we add the eight minutes and a half +delay we get 24 min. 10 sec., from which it is clear that the draper +won the race by twenty seconds. The majority of solvers make +forty-eight cuts to divide the roll into forty-eight pieces!</p> + +<hr style="width: 30%;" /> +<p><a name="X_35_JUDKINSS_CATTLEa" id="X_35_JUDKINSS_CATTLEa"></a><a href="#X_35_JUDKINSS_CATTLE"><b>35.—JUDKINS'S CATTLE.—<i>solution</i></b></a></p> + +<p>As there were five droves with an equal number of animals in each +drove, the number must be divisible by 5; and as every one of the +eight dealers bought the same number of animals, the number must be +divisible by 8. Therefore the number must be a multiple of 40. The +highest possible multiple of 40 that will work will be found to be +120, and this number could be made up in one of two ways—1 ox, 23 +pigs, and 96 sheep, or 3 oxen, 8 pigs, and 109 sheep. But the first is +excluded by the statement that the animals consisted of "oxen, pigs, +and sheep," because a single ox is not oxen. Therefore the second +grouping is the correct answer.</p> + +<hr style="width: 30%;" /> +<p><a name="X_36_BUYING_APPLESa" id="X_36_BUYING_APPLESa"></a><a href="#X_36_BUYING_APPLES"><b>36.—BUYING APPLES.—<i>solution</i></b></a></p> + +<p>As there were the same number of boys as girls, it is clear that the +number of children must be even, and, apart from a careful and exact +reading of the question, there would be three different answers. There +might be two, six, or fourteen children. In the first of these cases +there <span class='pagenum'>Pg 152<a name="Page_152" id="Page_152"></a></span>are ten different ways in which the apples could be bought. But +we were told there was an equal number of "boys and girls," and one +boy and one girl are not boys and girls, so this case has to be +excluded. In the case of fourteen children, the only possible +distribution is that each child receives one halfpenny apple. But we +were told that each child was to receive an equal distribution of +"apples," and one apple is not apples, so this case has also to be +excluded. We are therefore driven back on our third case, which +exactly fits in with all the conditions. Three boys and three girls +each receive 1 halfpenny apple and 2 third-penny apples. The value of +these 3 apples is one penny and one-sixth, which multiplied by six +makes sevenpence. Consequently, the correct answer is that there were +six children—three girls and three boys.</p> + +<hr style="width: 30%;" /> +<p><a name="X_37_BUYING_CHESTNUTSa" id="X_37_BUYING_CHESTNUTSa"></a><a href="#X_37_BUYING_CHESTNUTS"><b>37.—BUYING CHESTNUTS.—<i>solution</i></b></a></p> + +<p>In solving this little puzzle we are concerned with the exact +interpretation of the words used by the buyer and seller. I will give +the question again, this time adding a few words to make the matter +more clear. The added words are printed in italics.</p> + +<p>"A man went into a shop to buy chestnuts. He said he wanted a +pennyworth, and was given five chestnuts. 'It is not enough; I ought +to have a sixth <i>of a chestnut more</i>,' he remarked. 'But if I give you +one chestnut more,' the shopman replied, 'you will have <i>five-sixths</i> +too many.' Now, strange to say, they were both right. How many +chestnuts should the buyer receive for half a crown?"</p> + +<p>The answer is that the price was 155 chestnuts for half a crown. +Divide this number by 30, and we find that the buyer was entitled to +5<sup>1</sup>/<sub>6</sub> chestnuts in exchange for his penny. He was, therefore, right +when he said, after receiving five only, that he still wanted a sixth. +And the salesman was also correct in saying that if he gave one +chestnut more (that is, six chestnuts in all) he would be giving +five-sixths of a chestnut in excess.</p> + +<hr style="width: 30%;" /> +<p><a name="X_38_THE_BICYCLE_THIEFa" id="X_38_THE_BICYCLE_THIEFa"></a><a href="#X_38_THE_BICYCLE_THIEF"><b>38.—THE BICYCLE THIEF.—<i>solution</i></b></a></p> + +<p>People give all sorts of absurd answers to this question, and yet it +is perfectly simple if one just considers that the salesman cannot +possibly have lost more than the cyclist actually stole. The latter +rode away with a bicycle which cost the salesman eleven pounds, and +the ten pounds "change;" he thus made off with twenty-one pounds, in +exchange for a worthless bit of paper. This is the exact amount of the +salesman's loss, and the other operations of changing the cheque and +borrowing from a friend do not affect the question in the slightest. +The loss of prospective profit on the sale of the bicycle is, of +course, not direct loss of money out of pocket.</p> + +<hr style="width: 30%;" /> +<p><a name="X_39_THE_COSTERMONGERS_PUZZLEa" id="X_39_THE_COSTERMONGERS_PUZZLEa"></a><a href="#X_39_THE_COSTERMONGERS_PUZZLE"><b>39.—THE COSTERMONGER'S PUZZLE.—<i>solution</i></b></a></p> + +<p>Bill must have paid 8<i>s</i>. per hundred for his oranges—that is, 125 for +10<i>s</i>. At 8<i>s</i>. 4<i>d</i>. per hundred, he would only have received 120 oranges +for 10<i>s</i>. This exactly agrees with Bill's statement.</p> + +<hr style="width: 30%;" /> +<p><a name="X_40_MAMMAS_AGEa" id="X_40_MAMMAS_AGEa"></a><a href="#X_40_MAMMAS_AGE"><b>40.—MAMMA'S AGE.—<i>solution</i></b></a></p> + +<p>The age of Mamma must have been 29 years 2 months; that of Papa, 35 +years; and that of the child, Tommy, 5 years 10 months. Added +together, these make seventy years. The father is six times the age of +the son, and, after 23 years 4 months have elapsed, their united ages +will amount to 140 years, and Tommy will be just half the age of his +father.</p> + +<hr style="width: 30%;" /> +<p><a name="X_41_THEIR_AGESa" id="X_41_THEIR_AGESa"></a><a href="#X_41_THEIR_AGES"><b>41.—THEIR AGES.—<i>solution</i></b></a></p> + +<p>The gentleman's age must have been 54 years and that of his wife 45 +years.</p> + +<hr style="width: 30%;" /> +<p><a name="X_42_THE_FAMILY_AGESa" id="X_42_THE_FAMILY_AGESa"></a><a href="#X_42_THE_FAMILY_AGES"><b>42.—THE FAMILY AGES.—<i>solution</i></b></a></p> + +<p>The ages were as follows: Billie, 3½ years; Gertrude, 1¾ year; +Henrietta, 5¼ years; Charlie, 10½; years; and Janet, 21 years.</p> + +<hr style="width: 30%;" /> +<p><a name="X_43_MRS_TIMPKINSS_AGEa" id="X_43_MRS_TIMPKINSS_AGEa"></a><a href="#X_43_MRS_TIMPKINSS_AGE"><b>43.—MRS. TIMPKINS'S AGE.—<i>solution</i></b></a></p> + +<p>The age of the younger at marriage is always the same as the number of +years that expire before the elder becomes twice her age, if he was +three times as old at marriage. In our case it was eighteen years +afterwards; therefore Mrs. Timpkins was eighteen years of age on the +wedding-day, and her husband fifty-four.</p> + +<hr style="width: 30%;" /> +<p><a name="X_44_A_CENSUS_PUZZLEa" id="X_44_A_CENSUS_PUZZLEa"></a><a href="#X_44_A_CENSUS_PUZZLE"><b>44.—A CENSUS PUZZLE.—<i>solution</i></b></a></p> + +<p>Miss Ada Jorkins must have been twenty-four and her little brother +Johnnie three years of age, with thirteen brothers and sisters +between. There was a trap for the solver in the words "seven times +older than little Johnnie." Of course, "seven times older" is equal to +eight times as old. It is surprising how many people hastily assume +that it is the same as "seven times as old." Some of the best writers +have committed this blunder. Probably many of my readers thought that +the ages 24½ and 3½ were correct.</p> + +<hr style="width: 30%;" /> +<p><a name="X_45_MOTHER_AND_DAUGHTERa" id="X_45_MOTHER_AND_DAUGHTERa"></a><a href="#X_45_MOTHER_AND_DAUGHTER"><b>45.—MOTHER AND DAUGHTER.—<i>solution</i></b></a></p> + +<p>In four and a half years, when the daughter will be sixteen years and +a half and the mother forty-nine and a half years of age.</p> + +<hr style="width: 30%;" /> +<p><a name="X_46_MARY_AND_MARMADUKEa" id="X_46_MARY_AND_MARMADUKEa"></a><a href="#X_46_MARY_AND_MARMADUKE"><b>46.—MARY AND MARMADUKE.—<i>solution</i></b></a></p> + +<p>Marmaduke's age must have been twenty-nine years and two-fifths, and +Mary's nineteen years and three-fifths. When Marmaduke was aged +nineteen and three-fifths, Mary was only nine and four-fifths; so +Marmaduke was at that time twice her age.</p> + +<hr style="width: 30%;" /> +<p><a name="X_47_ROVERS_AGEa" id="X_47_ROVERS_AGEa"></a><a href="#X_47_ROVERS_AGE"><b>47.—ROVER'S AGE.—<i>solution</i></b></a></p> + +<p>Rover's present age is ten years and Mildred's thirty years. Five +years ago their respective <span class='pagenum'>Pg 153<a name="Page_153" id="Page_153"></a></span>ages were five and twenty-five. Remember +that we said "four times older than the dog," which is the same as +"five times as old." (See answer to No. <a href="#X_44_A_CENSUS_PUZZLEa">44</a>.)</p> + +<hr style="width: 30%;" /> +<p><a name="X_48_CONCERNING_TOMMYS_AGEa" id="X_48_CONCERNING_TOMMYS_AGEa"></a><a href="#X_48_CONCERNING_TOMMYS_AGE"><b>48.—CONCERNING TOMMY'S AGE.—<i>solution</i></b></a></p> + +<p>Tommy Smart's age must have been nine years and three-fifths. Ann's +age was sixteen and four-fifths, the mother's thirty-eight and +two-fifths, and the father's fifty and two-fifths.</p> + +<hr style="width: 30%;" /> +<p><a name="X_49_NEXT-DOOR_NEIGHBOURSa" id="X_49_NEXT-DOOR_NEIGHBOURSa"></a><a href="#X_49_NEXT-DOOR_NEIGHBOURS"><b>49.—NEXT-DOOR NEIGHBOURS.—<i>solution</i></b></a></p> + +<p>Mr. Jupp 39, Mrs. Jupp 34, Julia 14, and Joe 13; Mr. Simkin 42; Mrs. +Simkin 40; Sophy 10; and Sammy 8.</p> + +<hr style="width: 30%;" /> +<p><a name="X_50_THE_BAG_OF_NUTSa" id="X_50_THE_BAG_OF_NUTSa"></a><a href="#X_50_THE_BAG_OF_NUTS"><b>50.—THE BAG OF NUTS.—<i>solution</i></b></a></p> + +<p>It will be found that when Herbert takes twelve, Robert and +Christopher will take nine and fourteen respectively, and that they +will have together taken thirty-five nuts. As 35 is contained in 770 +twenty-two times, we have merely to multiply 12, 9, and 14 by 22 to +discover that Herbert's share was 264, Robert's 198, and Christopher's +308. Then, as the total of their ages is 17½ years or half the sum of +12, 9, and 14, their respective ages must be 6, 4½, and 7 years.</p> + +<hr style="width: 30%;" /> +<p><a name="X_51_HOW_OLD_WAS_MARYa" id="X_51_HOW_OLD_WAS_MARYa"></a><a href="#X_51_HOW_OLD_WAS_MARY"><b>51.—HOW OLD WAS MARY?—<i>solution</i></b></a></p> + +<p>The age of Mary to that of Ann must be as 5 to 3. And as the sum of +their ages was 44, Mary was 27½ and Ann 16½. One is exactly 11 years +older than the other. I will now insert in brackets in the original +statement the various ages specified: "Mary is (27½) twice as old as +Ann was (13¾) when Mary was half as old (24¾) as Ann will be (49½) +when Ann is three times as old (49½) as Mary was (16½) when Mary was +(16½) three times as old as Ann (5½)." Now, check this backwards. When +Mary was three times as old as Ann, Mary was 16½ and Ann 5½ (11 years +younger). Then we get 49½ for the age Ann will be when she is three +times as old as Mary was then. When Mary was half this she was 24¾. +And at that time Ann must have been 13¾ (11 years younger). Therefore +Mary is now twice as old—27½, and Ann 11 years younger—16½.</p> + +<hr style="width: 30%;" /> +<p><a name="X_52_QUEER_RELATIONSHIPSa" id="X_52_QUEER_RELATIONSHIPSa"></a><a href="#X_52_QUEER_RELATIONSHIPS"><b>52.—QUEER RELATIONSHIPS.—<i>solution</i></b></a></p> + +<p>If a man marries a woman, who dies, and he then marries his deceased +wife's sister and himself dies, it may be correctly said that he had +(previously) married the sister of his widow.</p> + +<p>The youth was not the nephew of Jane Brown, because he happened to be +her son. Her surname was the same as that of her brother, because she +had married a man of the same name as herself.</p> + +<hr style="width: 30%;" /> +<p><a name="X_53_HEARD_ON_THE_TUBE_RAILWAYa" id="X_53_HEARD_ON_THE_TUBE_RAILWAYa"></a><a href="#X_53_HEARD_ON_THE_TUBE_RAILWAY"><b>53.—HEARD ON THE TUBE RAILWAY.—<i>solution</i></b></a></p> + +<p>The gentleman was the second lady's uncle.</p> + +<hr style="width: 30%;" /> +<p><a name="X_54_A_FAMILY_PARTYa" id="X_54_A_FAMILY_PARTYa"></a><a href="#X_54_A_FAMILY_PARTY"><b>54.—A FAMILY PARTY.—<i>solution</i></b></a></p> + +<p>The party consisted of two little girls and a boy, their father and +mother, and their father's father and mother.</p> + +<hr style="width: 30%;" /> +<p><a name="X_55_A_MIXED_PEDIGREEa" id="X_55_A_MIXED_PEDIGREEa"></a><a href="#X_55_A_MIXED_PEDIGREE"><b>55.—A MIXED PEDIGREE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a055.png" width="400" height="280" alt="" title="" /> +</div> + +<p>The letter <i>m</i> stands for "married." It will be seen that John Snoggs +can say to Joseph Bloggs, "You are my <i>father's brother-in-law</i>, +because my father married your sister Kate; you are my <i>brother's +father-in-law</i>, because my brother Alfred married your daughter Mary; +and you are my <i>father-in-law's brother</i>, because my wife Jane was +your brother Henry's daughter."</p> + +<hr style="width: 30%;" /> +<p><a name="X_56_WILSONS_POSERa" id="X_56_WILSONS_POSERa"></a><a href="#X_56_WILSONS_POSER"><b>56.—WILSON'S POSER.—<i>solution</i></b></a></p> + +<p>If there are two men, each of whom marries the mother of the other, +and there is a son of each marriage, then each of such sons will be at +the same time uncle and nephew of the other. There are other ways in +which the relationship may be brought about, but this is the simplest.</p> + +<hr style="width: 30%;" /> +<p><a name="X_57_WHAT_WAS_THE_TIMEa" id="X_57_WHAT_WAS_THE_TIMEa"></a><a href="#X_57_WHAT_WAS_THE_TIME"><b>57.—WHAT WAS THE TIME?—<i>solution</i></b></a></p> + +<p>The time must have been 9.36 p.m. A quarter of the time since noon is +2 hr. 24 min., and a half of the time till noon next day is 7 hr. 12 +min. These added together make 9 hr. 36 min.</p> + +<hr style="width: 30%;" /> +<p><a name="X_58_A_TIME_PUZZLEa" id="X_58_A_TIME_PUZZLEa"></a><a href="#X_58_A_TIME_PUZZLE"><b>58.—A TIME PUZZLE.—<i>solution</i></b></a></p> + +<p>Twenty-six minutes.</p> + +<hr style="width: 30%;" /> +<p><a name="X_59_A_PUZZLING_WATCHa" id="X_59_A_PUZZLING_WATCHa"></a><a href="#X_59_A_PUZZLING_WATCH"><b>59.—A PUZZLING WATCH.—<i>solution</i></b></a></p> + +<p>If the 65 minutes be counted on the face of the same watch, then the +problem would be impossible: for the hands must coincide every 65<sup>5</sup>/<sub>11</sub> +minutes as shown by its face, and it matters not whether it runs fast +or slow; but if it is measured by true time, it gains <sup>5</sup>/<sub>11</sub> of a minute +in 65 minutes, or <sup>60</sup>/<sub>143</sub> of a minute per hour.</p> + +<hr style="width: 30%;" /> +<p><a name="X_60_THE_WAPSHAWS_WHARF_MYSTERYa" id="X_60_THE_WAPSHAWS_WHARF_MYSTERYa"></a><a href="#X_60_THE_WAPSHAWS_WHARF_MYSTERY"><b>60.—THE WAPSHAW'S WHARF MYSTERY.—<i>solution</i></b></a></p> + +<p>There are eleven different times in twelve hours when the hour and +minute hands of a clock are exactly one above the other. If we divide +12 <span class='pagenum'>Pg 154<a name="Page_154" id="Page_154"></a></span>hours by 11 we get 1 hr. 5 min. 27<sup>3</sup>/<sub>11</sub> sec., and this is the time +after twelve o'clock when they are first together, and also the time +that elapses between one occasion of the hands being together and the +next. They are together for the second time at 2 hr. 10 min. 54<sup>6</sup>/<sub>11</sub> +sec. (twice the above time); next at 3 hr. 16 min. 21<sup>9</sup>/<sub>11</sub> sec.; next +at 4 hr. 21 min. 49<sup>1</sup>/<sub>11</sub> sec. This last is the only occasion on which +the two hands are together with the second hand "just past the +forty-ninth second." This, then, is the time at which the watch must +have stopped. Guy Boothby, in the opening sentence of his <i>Across the +World for a Wife</i>, says, "It was a cold, dreary winter's afternoon, +and by the time the hands of the clock on my mantelpiece joined forces +and stood at twenty minutes past four, my chambers were well-nigh as +dark as midnight." It is evident that the author here made a slip, +for, as we have seen above, he is 1 min. 49<sup>1</sup>/<sub>11</sub> sec. out in his +reckoning.</p> + +<hr style="width: 30%;" /> +<p><a name="X_61_CHANGING_PLACESa" id="X_61_CHANGING_PLACESa"></a><a href="#X_61_CHANGING_PLACES"><b>61.—CHANGING PLACES.—<i>solution</i></b></a></p> + +<p>There are thirty-six pairs of times when the hands exactly change +places between three p.m. and midnight. The number of pairs of times +from any hour (<i>n</i>) to midnight is the sum of 12 - (<i>n</i> + 1) natural +numbers. In the case of the puzzle <i>n</i> = 3; therefore 12 - (3 + 1) = 8 +and 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 = 36, the required answer.</p> + +<p>The first pair of times is 3 hr. 21<sup>57</sup>/<sub>143</sub> min. and 4 hr. 16<sup>112</sup>/<sub>143</sub> +min., and the last pair is 10 hr. 59<sup>83</sup>/<sub>143</sub> min. and 11 hr. 54<sup>138</sup>/<sub>143</sub> +min. I will not give all the remainder of the thirty-six pairs of +times, but supply a formula by which any of the sixty-six pairs that +occur from midday to midnight may be at once found:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' rowspan='2'>a hr</td><td align='center' class='bb'>720b + 60a</td><td align='center' rowspan='2'>min. and b hr.</td><td align='center' class='bb'>720a + 60b min.</td></tr> +<tr><td align='center'>143</td><td align='center'>143</td></tr> +</table></div> + +<p>For the letter a may be substituted any hour from 0, 1, 2, 3 up to 10 +(where nought stands for 12 o'clock midday); and b may represent any +hour, later than a, up to 11.</p> + +<p>By the aid of this formula there is no difficulty in discovering the +answer to the second question: a = 8 and b = 11 will give the pair 8 +hr. 58<sup>106</sup>/<sub>143</sub> min. and 11 hr. 44<sup>128</sup>/<sub>143</sub> min., the latter being the +time when the minute hand is nearest of all to the point IX—in fact, +it is only <sup>15</sup>/<sub>143</sub> of a minute distant.</p> + +<p>Readers may find it instructive to make a table of all the sixty-six +pairs of times when the hands of a clock change places. An easy way is +as follows: Make a column for the first times and a second column for +the second times of the pairs. By making a = 0 and b = 1 in the above +expressions we find the first case, and enter hr. 5<sup>5</sup>/<sub>143</sub> min. at the +head of the first column, and 1 hr. 0<sup>60</sup>/<sub>143</sub> min. at the head of the +second column. Now, by successively adding 5<sup>5</sup>/<sub>143</sub> min. in the first, +and 1 hr. 0<sup>60</sup>/<sub>143</sub> min. in the second column, we get all the <i>eleven</i> +pairs in which the first time is a certain number of minutes after +nought, or mid-day. Then there is a "jump" in the times, but you can +find the next pair by making a = 1 and b = 2, and then by successively +adding these two times as before you will get all the <i>ten</i> pairs +after 1 o'clock. Then there is another "jump," and you will be able to +get by addition all the <i>nine</i> pairs after 2 o'clock. And so on to the +end. I will leave readers to investigate for themselves the nature and +cause of the "jumps." In this way we get under the successive hours, +11 + 10 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 = 66 pairs of times, which +result agrees with the formula in the first paragraph of this article.</p> + +<p>Some time ago the principal of a Civil Service Training College, who +conducts a "Civil Service Column" in one of the periodicals, had the +query addressed to him, "How soon after XII o'clock will a clock with +both hands of the same length be ambiguous?" His first answer was, +"Some time past one o'clock," but he varied the answer from issue to +issue. At length some of his readers convinced him that the answer is, +"At 5<sup>5</sup>/<sub>143</sub> min. past XII;" and this he finally gave as correct, +together with the reason for it that at that time <i>the time indicated +is the same whichever hand you may assume as hour hand!</i></p> + +<hr style="width: 30%;" /> +<p><a name="X_62_THE_CLUB_CLOCKa" id="X_62_THE_CLUB_CLOCKa"></a><a href="#X_62_THE_CLUB_CLOCK"><b>62.—THE CLUB CLOCK.—<i>solution</i></b></a></p> + +<p>The positions of the hands shown in the illustration could only +indicate that the clock stopped at 44 min. 51<sup>1143</sup>/<sub>1427</sub> sec. after +eleven o'clock. The second hand would next be "exactly midway between +the other two hands" at 45 min. 52<sup>496</sup>/<sub>1427</sub> sec. after eleven o'clock. +If we had been dealing with the points on the circle to which the +three hands are directed, the answer would be 45 min. 22<sup>106</sup>/<sub>1427</sub> sec. +after eleven; but the question applied to the hands, and the second +hand would not be between the others at that time, but outside them.</p> + +<hr style="width: 30%;" /> +<p><a name="X_63_THE_STOP-WATCHa" id="X_63_THE_STOP-WATCHa"></a><a href="#X_63_THE_STOP-WATCH"><b>63.—THE STOP-WATCH.—<i>solution</i></b></a></p> + +<p>The time indicated on the watch was 5<sup>5</sup>/<sub>11</sub> min. past 9, when the +second hand would be at 27<sup>3</sup>/<sub>11</sub> sec. The next time the hands would be +similar distances apart would be 54<sup>6</sup>/<sub>11</sub> min. past 2, when the second +hand would be at 32<sup>8</sup>/<sub>11</sub> sec. But you need only hold the watch (or our +previous illustration of it) in front of a mirror, when you will see +the second time reflected in it! Of course, when reflected, you will +read XI as I, X as II, and so on.</p> + +<hr style="width: 30%;" /> +<p><a name="X_64_THE_THREE_CLOCKSa" id="X_64_THE_THREE_CLOCKSa"></a><a href="#X_64_THE_THREE_CLOCKS"><b>64.—THE THREE CLOCKS.—<i>solution</i></b></a></p> + +<p>As a mere arithmetical problem this question presents no difficulty. +In order that the hands shall all point to twelve o'clock at the same +time, it is necessary that B shall gain at least twelve hours and that +C shall lose twelve hours. As B gains a minute in a day of twenty-four +hours, and C loses a minute in precisely the same time, it is evident +that one will have gained 720 minutes (just twelve hours) in 720 days, +and the other will have lost 720 minutes in 720 days. Clock A keeping +perfect time, all three clocks must indicate twelve o'clock +simultaneously at noon on the 720th day from April 1, 1898. What day +of the month will that be?</p> + +<p>I published this little puzzle in 1898 to see <span class='pagenum'>Pg 155<a name="Page_155" id="Page_155"></a></span>how many people were +aware of the fact that 1900 would not be a leap year. It was +surprising how many were then ignorant on the point. Every year that +can be divided by four without a remainder is bissextile or leap year, +with the exception that one leap year is cut off in the century. 1800 +was not a leap year, nor was 1900. On the other hand, however, to make +the calendar more nearly agree with the sun's course, every fourth +hundred year is still considered bissextile. Consequently, 2000, 2400, +2800, 3200, etc., will all be leap years. May my readers live to see +them. We therefore find that 720 days from noon of April 1, 1898, +brings us to noon of March 22, 1900.</p> + +<hr style="width: 30%;" /> +<p><a name="X_65_THE_RAILWAY_STATION_CLOCKa" id="X_65_THE_RAILWAY_STATION_CLOCKa"></a><a href="#X_65_THE_RAILWAY_STATION_CLOCK"><b>65.—THE RAILWAY STATION CLOCK.—<i>solution</i></b></a></p> + +<p>The time must have been 43<sup>7</sup>/<sub>11</sub> min. past two o'clock.</p> + +<hr style="width: 30%;" /> +<p><a name="X_66_THE_VILLAGE_SIMPLETONa" id="X_66_THE_VILLAGE_SIMPLETONa"></a><a href="#X_66_THE_VILLAGE_SIMPLETON"><b>66.—THE VILLAGE SIMPLETON.—<i>solution</i></b></a></p> + +<p>The day of the week on which the conversation took place was Sunday. +For when the day after to-morrow (Tuesday) is "yesterday," "to-day" +will be Wednesday; and when the day before yesterday (Friday) was +"to-morrow," "to-day" was Thursday. There are two days between +Thursday and Sunday, and between Sunday and Wednesday.</p> + +<hr style="width: 30%;" /> +<p><a name="X_67_AVERAGE_SPEEDa" id="X_67_AVERAGE_SPEEDa"></a><a href="#X_67_AVERAGE_SPEED"><b>67.—AVERAGE SPEED.—<i>solution</i></b></a></p> + +<p>The average speed is twelve miles an hour, not twelve and a half, as +most people will hastily declare. Take any distance you like, say +sixty miles. This would have taken six hours going and four hours +returning. The double journey of 120 miles would thus take ten hours, +and the average speed is clearly twelve miles an hour.</p> + +<hr style="width: 30%;" /> +<p><a name="X_68_THE_TWO_TRAINSa" id="X_68_THE_TWO_TRAINSa"></a><a href="#X_68_THE_TWO_TRAINS"><b>68.—THE TWO TRAINS.—<i>solution</i></b></a></p> + +<p>One train was running just twice as fast as the other.</p> + +<hr style="width: 30%;" /> +<p><a name="X_69_THE_THREE_VILLAGESa" id="X_69_THE_THREE_VILLAGESa"></a><a href="#X_69_THE_THREE_VILLAGES"><b>69.—THE THREE VILLAGES.—<i>solution</i></b></a></p> + +<p>Calling the three villages by their initial letters, it is clear that +the three roads form a triangle, A, B, C, with a perpendicular, +measuring twelve miles, dropped from C to the base A, B. This divides +our triangle into two right-angled triangles with a twelve-mile side +in common. It is then found that the distance from A to C is 15 miles, +from C to B 20 miles, and from A to B 25 (that is 9 and 16) miles. +These figures are easily proved, for the square of 12 added to the +square of 9 equals the square of 15, and the square of 12 added to the +square of 16 equals the square of 20.</p> + +<hr style="width: 30%;" /> +<p><a name="X_70_DRAWING_HER_PENSIONa" id="X_70_DRAWING_HER_PENSIONa"></a><a href="#X_70_DRAWING_HER_PENSION"><b>70.—DRAWING HER PENSION.—<i>solution</i></b></a></p> + +<p>The distance must be 6¾ miles.</p> + +<hr style="width: 30%;" /> +<p><a name="X_71_SIR_EDWYN_DE_TUDORa" id="X_71_SIR_EDWYN_DE_TUDORa"></a><a href="#X_71_SIR_EDWYN_DE_TUDOR"><b>71.—SIR EDWYN DE TUDOR.—<i>solution</i></b></a></p> + +<p>The distance must have been sixty miles. If Sir Edwyn left at noon and +rode 15 miles an hour, he would arrive at four o'clock—an hour too +soon. If he rode 10 miles an hour, he would arrive at six o'clock—an +hour too late. But if he went at 12 miles an hour, he would reach the +castle of the wicked baron exactly at five o'clock—the time +appointed.</p> + +<hr style="width: 30%;" /> +<p><a name="X_72_THE_HYDROPLANE_QUESTIONa" id="X_72_THE_HYDROPLANE_QUESTIONa"></a><a href="#X_72_THE_HYDROPLANE_QUESTION"><b>72.—THE HYDROPLANE QUESTION.—<i>solution</i></b></a></p> + +<p>The machine must have gone at the rate of seven-twenty-fourths of a +mile per minute and the wind travelled five-twenty-fourths of a mile +per minute. Thus, going, the wind would help, and the machine would do +twelve-twenty-fourths, or half a mile a minute, and returning only +two-twenty-fourths, or one-twelfth of a mile per minute, the wind +being against it. The machine without any wind could therefore do the +ten miles in thirty-four and two-sevenths minutes, since it could do +seven miles in twenty-four minutes.</p> + +<hr style="width: 30%;" /> +<p><a name="X_73_DONKEY_RIDINGa" id="X_73_DONKEY_RIDINGa"></a><a href="#X_73_DONKEY_RIDING"><b>73.—DONKEY RIDING.—<i>solution</i></b></a></p> + +<p>The complete mile was run in nine minutes. From the facts stated we +cannot determine the time taken over the first and second +quarter-miles separately, but together they, of course, took four and +a half minutes. The last two quarters were run in two and a quarter +minutes each.</p> + +<hr style="width: 30%;" /> +<p><a name="X_74_THE_BASKET_OF_POTATOESa" id="X_74_THE_BASKET_OF_POTATOESa"></a><a href="#X_74_THE_BASKET_OF_POTATOES"><b>74.—THE BASKET OF POTATOES.—<i>solution</i></b></a></p> + +<p>Multiply together the number of potatoes, the number less one, and +twice the number less one, then divide by 3. Thus 50, 49, and 99 +multiplied together make 242,550, which, divided by 3, gives us 80,850 +yards as the correct answer. The boy would thus have to travel 45 +miles and fifteen-sixteenths—a nice little recreation after a day's +work.</p> + +<hr style="width: 30%;" /> +<p><a name="X_75_THE_PASSENGERS_FAREa" id="X_75_THE_PASSENGERS_FAREa"></a><a href="#X_75_THE_PASSENGERS_FARE"><b>75.—THE PASSENGER'S FARE.—<i>solution</i></b></a></p> + +<p>Mr. Tompkins should have paid fifteen shillings as his correct share +of the motor-car fare. He only shared half the distance travelled for +£3, and therefore should pay half of thirty shillings, or fifteen +shillings.</p> + +<hr style="width: 30%;" /> +<p><a name="X_76_THE_BARREL_OF_BEERa" id="X_76_THE_BARREL_OF_BEERa"></a><a href="#X_76_THE_BARREL_OF_BEER"><b>76.—THE BARREL OF BEER.—<i>solution</i></b></a></p> + +<p>Here the digital roots of the six numbers are 6, 4, 1, 2, 7, 9, which +together sum to 29, whose digital root is 2. As the contents of the +barrels sold must be a number divisible by 3, if one buyer purchased +twice as much as the other, we must find a barrel with root 2, 5, or 8 +to set on one side. There is only one barrel, that containing 20 +gallons, that fulfils these conditions. So the man must have kept +these 20 gallons of beer for his own use and sold one man 33 gallons +(the 18-gallon and 15-gallon barrels) and sold the other man 66 +gallons (the 16, 19, and 31 gallon barrels).</p> + +<hr style="width: 30%;" /> +<p><a name="X_77_DIGITS_AND_SQUARESa" id="X_77_DIGITS_AND_SQUARESa"></a><a href="#X_77_DIGITS_AND_SQUARES"><b>77.—DIGITS AND SQUARES.—<i>solution</i></b></a></p> + +<p>The top row must be one of the four following numbers: 192, 219, 273, +327. The first was the example given.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 156<a name="Page_156" id="Page_156"></a></span><a name="X_78_ODD_AND_EVEN_DIGITSa" id="X_78_ODD_AND_EVEN_DIGITSa"></a><a href="#X_78_ODD_AND_EVEN_DIGITS"><b>78.—ODD AND EVEN DIGITS.—<i>solution</i></b></a></p> + +<p>As we have to exclude complex and improper fractions and recurring +decimals, the simplest solution is this: 79 + 5<sup>1</sup>/<sub>3</sub> and 84 + <sup>2</sup>/<sub>6</sub>, both +equal 84<sup>1</sup>/<sub>3</sub>. Without any use of fractions it is obviously impossible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_79_THE_LOCKERS_PUZZLEa" id="X_79_THE_LOCKERS_PUZZLEa"></a><a href="#X_79_THE_LOCKERS_PUZZLE"><b>79.—THE LOCKERS PUZZLE.—<i>solution</i></b></a></p> + +<p>The smallest possible total is 356 = 107 + 249, and the largest sum +possible is 981 = 235 + 746, or 657 + 324. The middle sum may be either 720 +=134+586, or 702 = 134 + 568, or 407 = 138 + 269. The total in this case must +be made up of three of the figures 0, 2, 4, 7, but no sum other than +the three given can possibly be obtained. We have therefore no choice +in the case of the first locker, an alternative in the case of the +third, and any one of three arrangements in the case of the middle +locker. Here is one solution:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>107</td><td align='center'>134</td><td align='center'>235</td></tr> +<tr><td align='center' class='bb'>249</td><td align='center' class='bb'>586</td><td align='center' class='bb'>746</td></tr> +<tr><td align='center'>356</td><td align='center'>720</td><td align='center'>981</td></tr> +</table></div> + +<p>Of course, in each case figures in the first two lines may be +exchanged vertically without altering the total, and as a result there +are just 3,072 different ways in which the figures might be actually +placed on the locker doors. I must content myself with showing one +little principle involved in this puzzle. The sum of the digits in the +total is always governed by the digit omitted. <sup>9</sup>/<sub>9</sub> - <sup>7</sup>/<sub>10</sub> - <sup>5</sup>/<sub>11</sub> - +<sup>3</sup>/<sub>12</sub> - <sup>1</sup>/<sub>13</sub> - <sup>8</sup>/<sub>14</sub> - <sup>6</sup>/<sub>15</sub> - <sup>4</sup>/<sub>16</sub> - <sup>2</sup>/<sub>17</sub> - <sup>0</sup>/<sub>18</sub>. Whichever digit shown +here in the upper line we omit, the sum of the digits in the total +will be found beneath it. Thus in the case of locker A we omitted 8, +and the figures in the total sum up to 14. If, therefore, we wanted to +get 356, we may know at once to a certainty that it can only be +obtained (if at all) by dropping the 8.</p> + +<hr style="width: 30%;" /> +<p><a name="X_80_THE_THREE_GROUPSa" id="X_80_THE_THREE_GROUPSa"></a><a href="#X_80_THE_THREE_GROUPS"><b>80.—THE THREE GROUPS.—<i>solution</i></b></a></p> + +<p>There are nine solutions to this puzzle, as follows, and no more:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>12 × 483 = 5,796</td></tr> +<tr><td align='center'>27 × 198 = 5,346</td></tr> +<tr><td align='center'>42 × 138 = 5,796</td></tr> +<tr><td align='center'>39 × 186 = 7,254</td></tr> +<tr><td align='center'>18 × 297 = 5,346</td></tr> +<tr><td align='center'>48 × 159 = 7,632</td></tr> +<tr><td align='center'>28 × 157 = 4,396</td></tr> +<tr><td align='center'>4 × 1,738 = 6,952</td></tr> +<tr><td align='center'>4 × 1,963 = 7,852</td></tr> +</table></div> + +<p>The seventh answer is the one that is most likely to be overlooked by +solvers of the puzzle.</p> + +<hr style="width: 30%;" /> +<p><a name="X_81_THE_NINE_COUNTERSa" id="X_81_THE_NINE_COUNTERSa"></a><a href="#X_81_THE_NINE_COUNTERS"><b>81.—THE NINE COUNTERS.—<i>solution</i></b></a></p> + +<p>In this case a certain amount of mere "trial" is unavoidable. But +there are two kinds of "trials"—those that are purely haphazard, and +those that are methodical. The true puzzle lover is never satisfied +with mere haphazard trials. The reader will find that by just +reversing the figures in 23 and 46 (making the multipliers 32 and 64) +both products will be 5,056. This is an improvement, but it is not the +correct answer. We can get as large a product as 5,568 if we multiply +174 by 32 and 96 by 58, but this solution is not to be found without +the exercise of some judgment and patience.</p> + +<hr style="width: 30%;" /> +<p><a name="X_82_THE_TEN_COUNTERSa" id="X_82_THE_TEN_COUNTERSa"></a><a href="#X_82_THE_TEN_COUNTERS"><b>82.—THE TEN COUNTERS.—<i>solution</i></b></a></p> + +<p>As I pointed out, it is quite easy so to arrange the counters that +they shall form a pair of simple multiplication sums, each of which +will give the same product—in fact, this can be done by anybody in +five minutes with a little patience. But it is quite another matter to +find that pair which gives the largest product and that which gives +the smallest product.</p> + +<p>Now, in order to get the smallest product, it is necessary to select +as multipliers the two smallest possible numbers. If, therefore, we +place 1 and 2 as multipliers, all we have to do is to arrange the +remaining eight counters in such a way that they shall form two +numbers, one of which is just double the other; and in doing this we +must, of course, try to make the smaller number as low as possible. Of +course the lowest number we could get would be 3,045; but this will +not work, neither will 3,405, 3,450, etc., and it may be ascertained +that 3,485 is the lowest possible. One of the required answers is +3,485 × 2 = 6,970, and 6,970 × 1 = 6,970.</p> + +<p>The other part of the puzzle (finding the pair with the highest +product) is, however, the real knotty point, for it is not at all easy +to discover whether we should let the multiplier consist of one or of +two figures, though it is clear that we must keep, so far as we can, +the largest figures to the left in both multiplier and multiplicand. +It will be seen that by the following arrangement so high a number as +58,560 may be obtained. Thus, 915 × 64 = 58,560, and 732 × 80 = 58,560.</p> + +<hr style="width: 30%;" /> +<p><a name="X_83_DIGITAL_MULTIPLICATIONa" id="X_83_DIGITAL_MULTIPLICATIONa"></a><a href="#X_83_DIGITAL_MULTIPLICATION"><b>83.—DIGITAL MULTIPLICATION.—<i>solution</i></b></a></p> + +<p>The solution that gives the smallest possible sum of digits in the +common product is 23 × 174 = 58 × 69 = 4,002, and the solution that gives the +largest possible sum of digits, 9 × 654 = 18 × 327 = 5,886. In the first case +the digits sum to 6 and in the second case to 27. There is no way of +obtaining the solution but by actual trial.</p> + +<hr style="width: 30%;" /> +<p><a name="X_84_THE_PIERROTS_PUZZLEa" id="X_84_THE_PIERROTS_PUZZLEa"></a><a href="#X_84_THE_PIERROTS_PUZZLE"><b>84.—THE PIERROT'S PUZZLE.—<i>solution</i></b></a></p> + +<p>There are just six different solutions to this puzzle, as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>8</td><td align='center'>multiplied by</td><td align='right'>473</td><td align='center'>equals</td><td align='right'>3784</td></tr> +<tr><td align='right'>9</td><td align='center'>"</td><td align='right'>351</td><td align='center'>"</td><td align='right'>3159</td></tr> +<tr><td align='right'>15</td><td align='center'>"</td><td align='right'>93</td><td align='center'>"</td><td align='right'>1395</td></tr> +<tr><td align='right'>21</td><td align='center'>"</td><td align='right'>87</td><td align='center'>"</td><td align='right'>1287</td></tr> +<tr><td align='right'>27</td><td align='center'>"</td><td align='right'>81</td><td align='center'>"</td><td align='right'>2187</td></tr> +<tr><td align='right'>35</td><td align='center'>"</td><td align='right'>41</td><td align='center'>"</td><td align='right'>1435</td></tr> +</table></div> + +<p>It will be seen that in every case the two multipliers contain exactly +the same figures as the product.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 157<a name="Page_157" id="Page_157"></a></span><a name="X_85_THE_CAB_NUMBERSa" id="X_85_THE_CAB_NUMBERSa"></a><a href="#X_85_THE_CAB_NUMBERS"><b>85.—THE CAB NUMBERS.—<i>solution</i></b></a></p> + +<p>The highest product is, I think, obtained by multiplying 8,745,231 by +96—namely, 839,542,176.</p> + +<p>Dealing here with the problem generally, I have shown in the last +puzzle that with three digits there are only two possible solutions, +and with four digits only six different solutions.</p> + +<p>These cases have all been given. With five digits there are just +twenty-two solutions, as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>3</td><td align='center'>x</td><td align='right'>4128</td><td align='center'>=</td><td align='right'>12384</td></tr> +<tr><td align='right'>3</td><td align='center'>x</td><td align='right'>4281</td><td align='center'>=</td><td align='right'>12843</td></tr> +<tr><td align='right'>3</td><td align='center'>x</td><td align='right'>7125</td><td align='center'>=</td><td align='right'>21375</td></tr> +<tr><td align='right'>3</td><td align='center'>x</td><td align='right'>7251</td><td align='center'>=</td><td align='right'>21753</td></tr> +<tr><td align='right'>2541</td><td align='center'>x</td><td align='right'>6</td><td align='center'>=</td><td align='right'>15246</td></tr> +<tr><td align='right'>651</td><td align='center'>x</td><td align='right'>24</td><td align='center'>=</td><td align='right'>15624</td></tr> +<tr><td align='right'>678</td><td align='center'>x</td><td align='right'>42</td><td align='center'>=</td><td align='right'>28476</td></tr> +<tr><td align='right'>246</td><td align='center'>x</td><td align='right'>51</td><td align='center'>=</td><td align='right'>12546</td></tr> +<tr><td align='right'>57</td><td align='center'>x</td><td align='right'>834</td><td align='center'>=</td><td align='right'>47538</td></tr> +<tr><td align='right'>75</td><td align='center'>x</td><td align='right'>231</td><td align='center'>=</td><td align='right'>17325</td></tr> +<tr><td align='right'>624</td><td align='center'>x</td><td align='right'>78</td><td align='center'>=</td><td align='right'>48672</td></tr> +<tr><td align='right'>435</td><td align='center'>x</td><td align='right'>87</td><td align='center'>=</td><td align='right'>37845</td></tr> +<tr><td align='center' colspan='5'>——————</td></tr> +<tr><td align='right'>9</td><td align='center'>x</td><td align='right'>7461</td><td align='center'>=</td><td align='right'>67149</td></tr> +<tr><td align='right'>72</td><td align='center'>x</td><td align='right'>936</td><td align='center'>=</td><td align='right'>67392</td></tr> +<tr><td align='center' colspan='5'>——————</td></tr> +<tr><td align='right'>2</td><td align='center'>x</td><td align='right'>8714</td><td align='center'>=</td><td align='right'>17428</td></tr> +<tr><td align='right'>2</td><td align='center'>x</td><td align='right'>8741</td><td align='center'>=</td><td align='right'>17482</td></tr> +<tr><td align='right'>65</td><td align='center'>x</td><td align='right'>281</td><td align='center'>=</td><td align='right'>18265</td></tr> +<tr><td align='right'>65</td><td align='center'>x</td><td align='right'>983</td><td align='center'>=</td><td align='right'>63985</td></tr> +<tr><td align='center' colspan='5'>——————</td></tr> +<tr><td align='right'>4973</td><td align='center'>x</td><td align='right'>8</td><td align='center'>=</td><td align='right'>39784</td></tr> +<tr><td align='right'>6521</td><td align='center'>x</td><td align='right'>8</td><td align='center'>=</td><td align='right'>52168</td></tr> +<tr><td align='right'>14</td><td align='center'>x</td><td align='right'>926</td><td align='center'>=</td><td align='right'>12964</td></tr> +<tr><td align='right'>86</td><td align='center'>x</td><td align='right'>251</td><td align='center'>=</td><td align='right'>21586</td></tr> +</table></div> + +<p>Now, if we took every possible combination and tested it by +multiplication, we should need to make no fewer than 30,240 trials, +or, if we at once rejected the number 1 as a multiplier, 28,560 +trials—a task that I think most people would be inclined to shirk. +But let us consider whether there be no shorter way of getting at the +results required. I have already explained that if you add together +the digits of any number and then, as often as necessary, add the +digits of the result, you must ultimately get a number composed of one +figure. This last number I call the "digital root." It is necessary in +every solution of our problem that the root of the sum of the digital +roots of our multipliers shall be the same as the root of their +product. There are only four ways in which this can happen: when the +digital roots of the multipliers are 3 and 6, or 9 and 9, or 2 and 2, +or 5 and 8. I have divided the twenty-two answers above into these +four classes. It is thus evident that the digital root of any product +in the first two classes must be 9, and in the second two classes 4.</p> + +<p>Owing to the fact that no number of five figures can have a digital +sum less than 15 or more than 35, we find that the figures of our +product must sum to either 18 or 27 to produce the root 9, and to +either 22 or 31 to produce the root 4. There are 3 ways of selecting +five different figures that add up to 18, there are 11 ways of +selecting five figures that add up to 27, there are 9 ways of +selecting five figures that add up to 22, and 5 ways of selecting five +figures that add up to 31. There are, therefore, 28 different groups, +and no more, from any one of which a product may be formed.</p> + +<p>We next write out in a column these 28 sets of five figures, and +proceed to tabulate the possible factors, or multipliers, into which +they may be split. Roughly speaking, there would now appear to be +about 2,000 possible cases to be tried, instead of the 30,240 +mentioned above; but the process of elimination now begins, and if the +reader has a quick eye and a clear head he can rapidly dispose of the +large bulk of these cases, and there will be comparatively few test +multiplications necessary. It would take far too much space to explain +my own method in detail, but I will take the first set of figures in +my table and show how easily it is done by the aid of little tricks +and dodges that should occur to everybody as he goes along.</p> + +<p>My first product group of five figures is 84,321. Here, as we have +seen, the root of each factor must be 3 or a multiple of 3. As there +is no 6 or 9, the only single multiplier is 3. Now, the remaining four +figures can be arranged in 24 different ways, but there is no need to +make 24 multiplications. We see at a glance that, in order to get a +five-figure product, either the 8 or the 4 must be the first figure to +the left. But unless the 2 is preceded on the right by the 8, it will +produce when multiplied either a 6 or a 7, which must not occur. We +are, therefore, reduced at once to the two cases, 3 × 4,128 and 3 × +4,281, both of which give correct solutions. Suppose next that we are +trying the two-figure factor, 21. Here we see that if the number to be +multiplied is under 500 the product will either have only four figures +or begin with 10. Therefore we have only to examine the cases 21 × 843 +and 21 × 834. But we know that the first figure will be repeated, and +that the second figure will be twice the first figure added to the +second. Consequently, as twice 3 added to 4 produces a nought in our +product, the first case is at once rejected. It only remains to try +the remaining case by multiplication, when we find it does not give a +correct answer. If we are next trying the factor 12, we see at the +start that neither the 8 nor the 3 can be in the units place, because +they would produce a 6, and so on. A sharp eye and an alert judgment +will enable us thus to run through our table in a much shorter time +than would be expected. The process took me a little more than three +hours.</p> + +<p>I have not attempted to enumerate the solutions in the cases of six, +seven, eight, and nine digits, but I have recorded nearly fifty +examples with nine digits alone.</p> + +<hr style="width: 30%;" /> +<p><a name="X_86_QUEER_MULTIPLICATIONa" id="X_86_QUEER_MULTIPLICATIONa"></a><a href="#X_86_QUEER_MULTIPLICATION"><b>86.—QUEER MULTIPLICATION.—<i>solution</i></b></a></p> + +<p>If we multiply 32547891 by 6, we get the product, 195287346. In both +cases all the nine digits are used once and once only.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 158<a name="Page_158" id="Page_158"></a></span><a name="X_87_THE_NUMBER_CHECKS_PUZZLEa" id="X_87_THE_NUMBER_CHECKS_PUZZLEa"></a><a href="#X_87_THE_NUMBER_CHECKS_PUZZLE"><b>87.—THE NUMBER CHECKS PUZZLE.—<i>solution</i></b></a></p> + +<p>Divide the ten checks into the following three groups: 7 1 5—4 6—3 2 +8 9 0, and the first multiplied by the second produces the third.</p> + +<hr style="width: 30%;" /> +<p><a name="X_88_DIGITAL_DIVISIONa" id="X_88_DIGITAL_DIVISIONa"></a><a href="#X_88_DIGITAL_DIVISION"><b>88.—DIGITAL DIVISION.—<i>solution</i></b></a></p> + +<p>It is convenient to consider the digits as arranged to form fractions +of the respective values, one-half, one-third, one-fourth, one-fifth, +one-sixth, one-seventh, one-eighth, and one-ninth. I will first give +the eight answers, as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'><sup>6729</sup>/<sub>13458</sub> = ½</td></tr> +<tr><td align='center'><sup>5823</sup>/<sub>17469</sub> = <sup>1</sup>/<sub>3</sub></td></tr> +<tr><td align='center'><sup>3942</sup>/<sub>15768</sub> = ¼</td></tr> +<tr><td align='center'><sup>2697</sup>/<sub>13485</sub> = <sup>1</sup>/<sub>5</sub></td></tr> +<tr><td align='center'><sup>2943</sup>/<sub>17658</sub> = <sup>1</sup>/<sub>6</sub></td></tr> +<tr><td align='center'><sup>2394</sup>/<sub>16758</sub> = <sup>1</sup>/<sub>7</sub></td></tr> +<tr><td align='center'><sup>3187</sup>/<sub>25496</sub> = <sup>1</sup>/<sub>8</sub></td></tr> +<tr><td align='center'><sup>6381</sup>/<sub>57429</sub> = <sup>1</sup>/<sub>9</sub></td></tr> +</table></div> + +<p>The sum of the numerator digits and the denominator digits will, of +course, always be 45, and the "digital root" is 9. Now, if we separate +the nine digits into any two groups, the sum of the two digital roots +will always be 9. In fact, the two digital roots must be either 9—9, +8—1, 7—2, 6—3, or 5—4. In the first case the actual sum is 18, but +then the digital root of this number is itself 9. The solutions in the +cases of one-third, one-fourth, one-sixth, one-seventh, and one-ninth +must be of the form 9—9; that is to say, the digital roots of both +numerator and denominator will be 9. In the cases of one-half and +one-fifth, however, the digital roots are 6—3, but of course the +higher root may occur either in the numerator or in the denominator; +thus <sup>2697</sup>/<sub>13485</sub>, <sup>2769</sup>/<sub>13845</sub>, <sup>2973</sup>/<sub>14865</sub>, <sup>3729</sup>/<sub>18645</sub>, where, in the +first two arrangements, the roots of the numerator and denominator are +respectively 6—3, and in the last two 3—6. The most curious case of +all is, perhaps, one-eighth, for here the digital roots may be of any +one of the five forms given above.</p> + +<p>The denominators of the fractions being regarded as the numerators +multiplied by 2, 3, 4, 5, 6, 7, 8, and 9 respectively, we must pay +attention to the "carryings over." In order to get five figures in the +product there will, of course, always be a carry-over after +multiplying the last figure to the left, and in every case higher than +4 we must carry over at least three times. Consequently in cases from +one-fifth to one-ninth we cannot produce different solutions by a mere +change of position of pairs of figures, as, for example, we may with +<sup>5832</sup>/<sub>17496</sub> and <sup>5823</sup>/<sub>17469</sub>, where the <sup>2</sup>/<sub>6</sub> and <sup>3</sup>/<sub>9</sub> change places. It is +true that the same figures may often be differently arranged, as shown +in the two pairs of values for one-fifth that I have given in the last +paragraph, but here it will be found there is a general readjustment +of figures and not a simple changing of the positions of pairs. There +are other little points that would occur to every solver—such as that +the figure 5 cannot ever appear to the extreme right of the numerator, +as this would result in our getting either a nought or a second 5 in +the denominator. Similarly 1 cannot ever appear in the same position, +nor 6 in the fraction one-sixth, nor an even figure in the fraction +one-fifth, and so on. The preliminary consideration of such points as +I have touched upon will not only prevent our wasting a lot of time in +trying to produce impossible forms, but will lead us more or less +directly to the desired solutions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_89_ADDING_THE_DIGITSa" id="X_89_ADDING_THE_DIGITSa"></a><a href="#X_89_ADDING_THE_DIGITS"><b>89.—ADDING THE DIGITS.—<i>solution</i></b></a></p> + +<p>The smallest possible sum of money is £1, 8<i>s</i>. 9¾d., the digits of +which add to 25.</p> + +<hr style="width: 30%;" /> +<p><a name="X_90_THE_CENTURY_PUZZLEa" id="X_90_THE_CENTURY_PUZZLEa"></a><a href="#X_90_THE_CENTURY_PUZZLE"><b>90.—THE CENTURY PUZZLE.—<i>solution</i></b></a></p> + +<p>The problem of expressing the number 100 as a mixed number or +fraction, using all the nine digits once, and once only, has, like all +these digital puzzles, a fascinating side to it. The merest tyro can +by patient trial obtain correct results, and there is a singular +pleasure in discovering and recording each new arrangement akin to the +delight of the botanist in finding some long-sought plant. It is +simply a matter of arranging those nine figures correctly, and yet +with the thousands of possible combinations that confront us the task +is not so easy as might at first appear, if we are to get a +considerable number of results. Here are eleven answers, including the +one I gave as a specimen:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>96<sup>2148</sup>/<sub>537</sub></td></tr> +<tr><td align='center'>96<sup>1752</sup>/<sub>438</sub></td></tr> +<tr><td align='center'>96<sup>1428</sup>/<sub>357</sub></td></tr> +<tr><td align='center'>94<sup>1578</sup>/<sub>263</sub></td></tr> +<tr><td align='center'>91<sup>7524</sup>/<sub>836</sub></td></tr> +<tr><td align='center'>91<sup>5823</sup>/<sub>647</sub></td></tr> +<tr><td align='center'>91<sup>5742</sup>/<sub>638</sub></td></tr> +<tr><td align='center'>82<sup>3546</sup>/<sub>197</sub></td></tr> +<tr><td align='center'>81<sup>7524</sup>/<sub>396</sub></td></tr> +<tr><td align='center'>81<sup>5643</sup>/<sub>297</sub></td></tr> +<tr><td align='center'>3<sup>69258</sup>/<sub>714</sub></td></tr> +</table></div> + +<p>Now, as all the fractions necessarily represent whole numbers, it will +be convenient to deal with them in the following form: 96 + 4, 94 + 6, +91 + 9, 82 + 18, 81 + 19, and 3 + 97.</p> + +<p>With any whole number the digital roots of the fraction that brings it +up to 100 will always be of one particular form. Thus, in the case of +96 + 4, one can say at once that if any answers are obtainable, then +the roots of both the numerator and the denominator of the fraction +will be 6. Examine the first three arrangements given above, and you +will find that this is so. In the case of 94 + 6 the roots of the +numerator and denominator will be respectively 3—2, in the case of 91 ++ 9 and of 82 + 18 they will be 9—8, in the case of 81 + 19 they will +be 9—9, and in the case of 3 + 97 they will be 3—3. Every fraction +that can be employed has, therefore, its particular digital root form, +and you are only wasting your time in unconsciously attempting to +break through this law.</p> + +<p>Every reader will have perceived that certain whole numbers are +evidently impossible. Thus, if there is a 5 in the whole number, there +will also be a nought or a second 5 in the fraction, which are barred +by the conditions. Then multiples of 10, such as 90 and 80, cannot of +course occur, nor can the whole number conclude with a 9, like 89 and +79, because the fraction, equal to 11 or 21, will have 1 in the last +place, and will therefore repeat a figure. Whole numbers that repeat a +figure, such as 88 and 77, are also clearly useless. These cases, as I +have said, are all obvious to every reader. But when I declare <span class='pagenum'>Pg 159<a name="Page_159" id="Page_159"></a></span>that +such combinations as 98 + 2, 92 + 8, 86 + 14, 83 + 17, 74 + 26, etc., +etc., are to be at once dismissed as impossible, the reason is not so +evident, and I unfortunately cannot spare space to explain it.</p> + +<p>But when all those combinations have been struck out that are known to +be impossible, it does not follow that all the remaining "possible +forms" will actually work. The elemental form may be right enough, but +there are other and deeper considerations that creep in to defeat our +attempts. For example, 98 + 2 is an impossible combination, because we +are able to say at once that there is no possible form for the digital +roots of the fraction equal to 2. But in the case of 97 + 3 there is a +possible form for the digital roots of the fraction, namely, 6—5, and +it is only on further investigation that we are able to determine that +this form cannot in practice be obtained, owing to curious +considerations. The working is greatly simplified by a process of +elimination, based on such considerations as that certain +multiplications produce a repetition of figures, and that the whole +number cannot be from 12 to 23 inclusive, since in every such case +sufficiently small denominators are not available for forming the +fractional part.</p> + +<hr style="width: 30%;" /> +<p><a name="X_91_MORE_MIXED_FRACTIONSa" id="X_91_MORE_MIXED_FRACTIONSa"></a><a href="#X_91_MORE_MIXED_FRACTIONS"><b>91.—MORE MIXED FRACTIONS.—<i>solution</i></b></a></p> + +<p>The point of the present puzzle lies in the fact that the numbers 15 +and 18 are not capable of solution. There is no way of determining +this without trial. Here are answers for the ten possible numbers:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>9<sup>5472</sup>/<sub>1368</sub></td><td align='center'>=</td><td align='right'>13;</td></tr> +<tr><td align='right'>9<sup>6435</sup>/<sub>1287</sub></td><td align='center'>=</td><td align='right'>14;</td></tr> +<tr><td align='right'>12<sup>3576</sup>/<sub>894</sub></td><td align='center'>=</td><td align='right'>16;</td></tr> +<tr><td align='right'>6<sup>13258</sup>/<sub>947</sub></td><td align='center'>=</td><td align='right'>20;</td></tr> +<tr><td align='right'>15<sup>9432</sup>/<sub>786</sub></td><td align='center'>=</td><td align='right'>27;</td></tr> +<tr><td align='right'>24<sup>9756</sup>/<sub>813</sub></td><td align='center'>=</td><td align='right'>36;</td></tr> +<tr><td align='right'>27<sup>5148</sup>/<sub>396</sub></td><td align='center'>=</td><td align='right'>40;</td></tr> +<tr><td align='right'>65<sup>1892</sup>/<sub>473</sub></td><td align='center'>=</td><td align='right'>69;</td></tr> +<tr><td align='right'>59<sup>3614</sup>/<sub>278</sub></td><td align='center'>=</td><td align='right'>72;</td></tr> +<tr><td align='right'>75<sup>3648</sup>/<sub>192</sub></td><td align='center'>=</td><td align='right'>94.</td></tr> +</table></div> + +<p>I have only found the one arrangement for each of the numbers 16, 20, +and 27; but the other numbers are all capable of being solved in more +than one way. As for 15 and 18, though these may be easily solved as a +simple fraction, yet a "mixed fraction" assumes the presence of a +whole number; and though my own idea for dodging the conditions is the +following, where the fraction is both complex and mixed, it will be +fairer to keep exactly to the form indicated:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>3<sup>8952</sup>/<span style="font-size: smaller;">746</span>/<sub>1</sub> = 15</td></tr> +<tr><td align='center'>9<sup>5742</sup>/<span style="font-size: smaller;">638</span>/<sub>1</sub> = 18</td></tr> +</table></div> + +<p>I have proved the possibility of solution for all numbers up to 100, +except 1, 2, 3, 4, 15, and 18. The first three are easily shown to be +impossible. I have also noticed that numbers whose digital root is +8—such as 26, 35, 44, 53, etc.—seem to lend themselves to the +greatest number of answers. For the number 26 alone I have recorded no +fewer than twenty-five different arrangements, and I have no doubt +that there are many more.</p> + +<hr style="width: 30%;" /> +<p><a name="X_92_DIGITAL_SQUARE_NUMBERSa" id="X_92_DIGITAL_SQUARE_NUMBERSa"></a><a href="#X_92_DIGITAL_SQUARE_NUMBERS"><b>92.—DIGITAL SQUARE NUMBERS.—<i>solution</i></b></a></p> + +<p>So far as I know, there are no published tables of square numbers that +go sufficiently high to be available for the purposes of this puzzle. +The lowest square number containing all the nine digits once, and once +only, is 139,854,276, the square of 11,826. The highest square number +under the same conditions is, 923,187,456, the square of 30,384.</p> + +<hr style="width: 30%;" /> +<p><a name="X_93_THE_MYSTIC_ELEVENa" id="X_93_THE_MYSTIC_ELEVENa"></a><a href="#X_93_THE_MYSTIC_ELEVEN"><b>93—THE MYSTIC ELEVEN.—<i>solution</i></b></a></p> + +<p>Most people know that if the sum of the digits in the odd places of +any number is the same as the sum of the digits in the even places, +then the number is divisible by 11 without remainder. Thus in +896743012 the odd digits, 20468, add up 20, and the even digits, 1379, +also add up 20. Therefore the number may be divided by 11. But few +seem to know that if the difference between the sum of the odd and the +even digits is 11, or a multiple of 11, the rule equally applies. This +law enables us to find, with a very little trial, that the smallest +number containing nine of the ten digits (calling nought a digit) that +is divisible by 11 is 102,347,586, and the highest number possible, +987,652,413.</p> + +<hr style="width: 30%;" /> +<p><a name="X_94_THE_DIGITAL_CENTURYa" id="X_94_THE_DIGITAL_CENTURYa"></a><a href="#X_94_THE_DIGITAL_CENTURY"><b>94.—THE DIGITAL CENTURY.—<i>solution</i></b></a></p> + +<p>There is a very large number of different ways in which arithmetical +signs may be placed between the nine digits, arranged in numerical +order, so as to give an expression equal to 100. In fact, unless the +reader investigated the matter very closely, he might not suspect that +so many ways are possible. It was for this reason that I added the +condition that not only must the fewest possible signs be used, but +also the fewest possible strokes. In this way we limit the problem to +a single solution, and arrive at the simplest and therefore (in this +case) the best result.</p> + +<p>Just as in the case of magic squares there are methods by which we may +write down with the greatest ease a large number of solutions, but not +all the solutions, so there are several ways in which we may quickly +arrive at dozens of arrangements of the "Digital Century," without +finding all the possible arrangements. There is, in fact, very little +principle in the thing, and there is no certain way of demonstrating +that we have got the best possible solution. All I can say is that the +arrangement I shall give as the best is the best I have up to the +present succeeded in discovering. I will give the reader a few +interesting specimens, the first being the solution usually published, +and the last the best solution that I know.</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'></td><td align='center'>Signs.</td><td align='center'></td><td align='center'>Strokes.</td></tr> +<tr><td align='right'>1 + 2 + 3 + 4 + 5 + 6 + 7 + (8 × 9) = 100</td><td align='center'>( 9</td><td align='center'>..</td><td align='center'>18)</td></tr> +<tr><td align='right'>(1 × 2) - 3 - 4 - 5 + (6 × 7) + (8 × 9) = 100</td><td align='center'>(12</td><td align='center'>..</td><td align='center'>20)</td></tr> +<tr><td align='right'>1 + (2 × 3) + (4 × 5) - 6 + 7 + (8 × 9) = 100</td><td align='center'>(11</td><td align='center'>..</td><td align='center'>21)</td></tr> +<tr><td align='right'>(1 + 2 - 3 - 4)(5 - 6 - 7 - 8 - 9) = 100</td><td align='center'>( 9</td><td align='center'>..</td><td align='center'>12)</td></tr> +<tr><td align='right'>1 + (2 × 3) + 4 + 5 + 67 + 8 + 9 = 100</td><td align='center'>(8</td><td align='center'>..</td><td align='center'>16)</td></tr> +<tr><td align='right'>(1 × 2) + 34 + 56 + 7 - 8 + 9 = 100</td><td align='center'>(7</td><td align='center'>..</td><td align='center'>13)</td></tr> +<tr><td align='right'>12 + 3 - 4 + 5 + 67 + 8 + 9 = 100</td><td align='center'>(6</td><td align='center'>..</td><td align='center'>11)</td></tr> +<tr><td align='right'>123 - 4 - 5 - 6 - 7 + 8 - 9 = 100</td><td align='center'>(6</td><td align='center'>..</td><td align='center'>7)</td></tr> +<tr><td align='right'>123 + 4 - 5 + 67 - 8 - 9 = 100</td><td align='center'>(4</td><td align='center'>..</td><td align='center'>6)</td></tr> +<tr><td align='right'>123 + 45 - 67 + 8 - 9 = 100</td><td align='center'>(4</td><td align='center'>..</td><td align='center'>6)</td></tr> +<tr><td align='right'>123 - 45 - 67 + 89 = 100</td><td align='center'>(3</td><td align='center'>..</td><td align='center'>4)</td></tr> +</table></div> + +<p><span class='pagenum'>Pg 160<a name="Page_160" id="Page_160"></a></span></p> +<p>It will be noticed that in the above I have counted the bracket as one +sign and two strokes. The last solution is singularly simple, and I do +not think it will ever be beaten.</p> + +<hr style="width: 30%;" /> +<p><a name="X_95_THE_FOUR_SEVENSa" id="X_95_THE_FOUR_SEVENSa"></a><a href="#X_95_THE_FOUR_SEVENS"><b>95.—THE FOUR SEVENS.—<i>solution</i></b></a></p> + +<p>The way to write four sevens with simple arithmetical signs so that +they represent 100 is as follows:—</p> + +<div class='center'> +<sup>7</sup>/<sub>.7</sub>×<sup>7</sup>/<sub>.7</sub> = 100. +</div> + +<p>Of course the fraction, 7 over decimal 7, equals 7 divided by <sup>7</sup>/<sub>10</sub>, +which is the same as 70 divided by 7, or 10. Then 10 multiplied by 10 +is 100, and there you are! It will be seen that this solution applies +equally to any number whatever that you may substitute for 7.</p> + +<hr style="width: 30%;" /> +<p><a name="X_96_THE_DICE_NUMBERSa" id="X_96_THE_DICE_NUMBERSa"></a><a href="#X_96_THE_DICE_NUMBERS"><b>96.—THE DICE NUMBERS.—<i>solution</i></b></a></p> + +<p>The sum of all the numbers that can be formed with any given set of +four different figures is always 6,666 multiplied by the sum of the +four figures. Thus, 1, 2, 3, 4 add up 10, and ten times 6,666 is +66,660. Now, there are thirty-five different ways of selecting four +figures from the seven on the dice—remembering the 6 and 9 trick. The +figures of all these thirty-five groups add up to 600. Therefore 6,666 +multiplied by 600 gives us 3,999,600 as the correct answer.</p> + +<p>Let us discard the dice and deal with the problem generally, using the +nine digits, but excluding nought. Now, if you were given simply the +sum of the digits—that is, if the condition were that you could use +any four figures so long as they summed to a given amount—then we +have to remember that several combinations of four digits will, in +many cases, make the same sum.</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'></td><td align='center'>10</td><td align='center'>11</td><td align='center'>12</td><td align='center'>13</td><td align='center'>14</td><td align='center'>15</td><td align='center'>16</td><td align='center'>17</td><td align='center'>18</td><td align='center'>19</td><td align='center'>20</td></tr> +<tr><td align='center'></td><td align='center'>1</td><td align='center'>1</td><td align='center'>2</td><td align='center'>3</td><td align='center'>5</td><td align='center'>6</td><td align='center'>8</td><td align='center'>9</td><td align='center'>11</td><td align='center'>11</td><td align='center'>12</td></tr> +<tr><td> </td></tr> +<tr><td align='center'></td><td align='center'>21</td><td align='center'>22</td><td align='center'>23</td><td align='center'>24</td><td align='center'>25</td><td align='center'>26</td><td align='center'>27</td><td align='center'>28</td><td align='center'>29</td><td align='center'>30</td></tr> +<tr><td align='center'></td><td align='center'>11</td><td align='center'>11</td><td align='center'>9</td><td align='center'>8</td><td align='center'>6</td><td align='center'>5</td><td align='center'>3</td><td align='center'>2</td><td align='center'>1</td><td align='center'>1</td></tr> +</table></div> + +<p>Here the top row of numbers gives all the possible sums of four +different figures, and the bottom row the number of different ways in +which each sum may be made. For example 13 may be made in three ways: +1237, 1246, and 1345. It will be found that the numbers in the bottom +row add up to 126, which is the number of combinations of nine figures +taken four at a time. From this table we may at once calculate the +answer to such a question as this: What is the sum of all the numbers +composed of our different digits (nought excluded) that add up to 14? +Multiply 14 by the number beneath t in the table, 5, and multiply the +result by 6,666, and you will have the answer. It follows that, to +know the sum of all the numbers composed of four different digits, if +you multiply all the pairs in the two rows and then add the results +together, you will get 2,520, which, multiplied by 6,666, gives the +answer 16,798,320.</p> + +<p>The following general solution for any number of digits will +doubtless interest readers. Let n represent number of digits, then 5 +(10<sup>n</sup> - 1) ) 8! divided by (9 - n)! equals the required sum. +Note that 0! equals 1. This may be reduced to the following practical +rule: Multiply together 4 × 7 × 6 × 5 ... to (n - 1) +factors; now add (n + 1) ciphers to the right, and from this result +subtract the same set of figures with a single cipher to the right. Thus +for n = 4 (as in the case last mentioned), 4 × 7 × 6 = 168. +Therefore 16,800,000 less 1,680 gives us 16,798,320 in another way.</p> + +<hr style="width: 30%;" /> +<p><a name="X_97_THE_SPOT_ON_THE_TABLEa" id="X_97_THE_SPOT_ON_THE_TABLEa"></a><a href="#X_97_THE_SPOT_ON_THE_TABLE"><b>97.—THE SPOT ON THE TABLE.—<i>solution</i></b></a></p> + +<p>The ordinary schoolboy would correctly treat this as a quadratic +equation. Here is the actual arithmetic. Double the product of the two +distances from the walls. This gives us 144, which is the square of +12. The sum of the two distances is 17. If we add these two numbers, +12 and 17, together, and also subtract one from the other, we get the +two answers that 29 or 5 was the radius, or half-diameter, of the +table. Consequently, the full diameter was 58 in. or 10 in. But a +table of the latter dimensions would be absurd, and not at all in +accordance with the illustration. Therefore the table must have been +58 in. in diameter. In this case the spot was on the edge nearest to +the corner of the room—to which the boy was pointing. If the other +answer were admissible, the spot would be on the edge farthest from +the corner of the room.</p> + +<hr style="width: 30%;" /> +<p><a name="X_98_ACADEMIC_COURTESIESa" id="X_98_ACADEMIC_COURTESIESa"></a><a href="#X_98_ACADEMIC_COURTESIES"><b>98.—ACADEMIC COURTESIES.—<i>solution</i></b></a></p> + +<p>There must have been ten boys and twenty girls. The number of bows +girl to girl was therefore 380, of boy to boy 90, of girl with boy +400, and of boys and girls to teacher 30, making together 900, as +stated. It will be remembered that it was not said that the teacher +himself returned the bows of any child.</p> + +<hr style="width: 30%;" /> +<p><a name="X_99_THE_THIRTY-THREE_PEARLSa" id="X_99_THE_THIRTY-THREE_PEARLSa"></a><a href="#X_99_THE_THIRTY-THREE_PEARLS"><b>99.—THE THIRTY-THREE PEARLS.—<i>solution</i></b></a></p> + +<p>The value of the large central pearl must have been £3,000. The pearl +at one end (from which they increased in value by £100) was £1,400; +the pearl at the other end, £600.</p> + +<hr style="width: 30%;" /> +<p><a name="X_100_THE_LABOURERS_PUZZLEa" id="X_100_THE_LABOURERS_PUZZLEa"></a><a href="#X_100_THE_LABOURERS_PUZZLE"><b>100.—THE LABOURER'S PUZZLE.—<i>solution</i></b></a></p> + +<p>The man said, "I am going twice as deep," not "as deep again." That is +to say, he was still going twice as deep as he had gone already, so +<span class='pagenum'>Pg 161<a name="Page_161" id="Page_161"></a></span>that when finished the hole would be three times its present depth. +Then the answer is that at present the hole is 3 ft. 6 in. deep and +the man 2 ft. 4 in. above ground. When completed the hole will be 10 +ft. 6 in. deep, and therefore the man will then be 4 ft. 8 in. below +the surface, or twice the distance that he is now above ground.</p> + +<hr style="width: 30%;" /> +<p><a name="X_101_THE_TRUSSES_OF_HAYa" id="X_101_THE_TRUSSES_OF_HAYa"></a><a href="#X_101_THE_TRUSSES_OF_HAY"><b>101.—THE TRUSSES OF HAY.—<i>solution</i></b></a></p> + +<p>Add together the ten weights and divide by 4, and we get 289 lbs. as +the weight of the five trusses together. If we call the five trusses +in the order of weight A, B, C, D, and E, the lightest being A and the +heaviest E, then the lightest, no lbs., must be the weight of A and B; +and the next lightest, 112 lbs., must be the weight of A and C. Then +the two heaviest, D and E, must weigh 121 lbs., and C and E must weigh +120 lbs. We thus know that A, B, D, and E weigh together 231 lbs., +which, deducted from 289 lbs. (the weight of the five trusses), gives +us the weight of C as 58 lbs. Now, by mere subtraction, we find the +weight of each of the five trusses—54 lbs., 56 lbs., 58 lbs., 59 +lbs., and 62 lbs. respectively.</p> + +<hr style="width: 30%;" /> +<p><a name="X_102_MR_GUBBINS_IN_A_FOGa" id="X_102_MR_GUBBINS_IN_A_FOGa"></a><a href="#X_102_MR_GUBBINS_IN_A_FOG"><b>102.—MR. GUBBINS IN A FOG.—<i>solution</i></b></a></p> + +<p>The candles must have burnt for three hours and three-quarters. One +candle had one-sixteenth of its total length left and the other +four-sixteenths.</p> + +<hr style="width: 30%;" /> +<p><a name="X_103_PAINTING_THE_LAMP-POSTSa" id="X_103_PAINTING_THE_LAMP-POSTSa"></a><a href="#X_103_PAINTING_THE_LAMP-POSTS"><b>103.—PAINTING THE LAMP-POSTS.—<i>solution</i></b></a></p> + +<p>Pat must have painted six more posts than Tim, no matter how many +lamp-posts there were. For example, suppose twelve on each side; then +Pat painted fifteen and Tim nine. If a hundred on each side, Pat +painted one hundred and three, and Tim only ninety-seven</p> + +<hr style="width: 30%;" /> +<p><a name="X_104_CATCHING_THE_THIEFa" id="X_104_CATCHING_THE_THIEFa"></a><a href="#X_104_CATCHING_THE_THIEF"><b>104.—CATCHING THE THIEF.—<i>solution</i></b></a></p> + +<p>The constable took thirty steps. In the same time the thief would take +forty-eight, which, added to his start of twenty-seven, carried him +seventy-five steps. This distance would be exactly equal to thirty +steps of the constable.</p> + +<hr style="width: 30%;" /> +<p><a name="X_105_THE_PARISH_COUNCIL_ELECTIONa" id="X_105_THE_PARISH_COUNCIL_ELECTIONa"></a><a href="#X_105_THE_PARISH_COUNCIL_ELECTION"><b>105.—THE PARISH COUNCIL ELECTION,—<i>solution</i></b></a></p> + +<p>The voter can vote for one candidate in 23 ways, for two in 253 ways, +for three in 1,771, for four in 8,855, for five in 33,649, for six in +100,947, for seven in 245,157, for eight in 490,314, and for nine +candidates in 817,190 different ways. Add these together, and we get +the total of 1,698,159 ways of voting.</p> + +<hr style="width: 30%;" /> +<p><a name="X_106_THE_MUDDLETOWN_ELECTIONa" id="X_106_THE_MUDDLETOWN_ELECTIONa"></a><a href="#X_106_THE_MUDDLETOWN_ELECTION"><b>106.—THE MUDDLETOWN ELECTION.—<i>solution</i></b></a></p> + +<p>The numbers of votes polled respectively by the Liberal, the +Conservative, the Independent, and the Socialist were 1,553, 1,535, +1,407, and 978 All that was necessary was to add the sum of the three +majorities (739) to the total poll of 5,473 (making 6,212) and divide +by 4, which gives us 1,553 as the poll of the Liberal. Then the polls +of the other three candidates can, of course, be found by deducting +the successive majorities from the last-mentioned number.</p> + +<hr style="width: 30%;" /> +<p><a name="X_107_THE_SUFFRAGISTS_MEETINGa" id="X_107_THE_SUFFRAGISTS_MEETINGa"></a><a href="#X_107_THE_SUFFRAGISTS_MEETING"><b>107.—THE SUFFRAGISTS' MEETING.—<i>solution</i></b></a></p> + +<p>Eighteen were present at the meeting and eleven left. If twelve had +gone, two-thirds would have retired. If only nine had gone, the +meeting would have lost half its members.</p> + +<hr style="width: 30%;" /> +<p><a name="X_108_THE_LEAP-YEAR_LADIESa" id="X_108_THE_LEAP-YEAR_LADIESa"></a><a href="#X_108_THE_LEAP-YEAR_LADIES"><b>108.—THE LEAP-YEAR LADIES.—<i>solution</i></b></a></p> + +<p>The correct and only answer is that 11,616 ladies made proposals of +marriage. Here are all the details, which the reader can check for +himself with the original statements. Of 10,164 spinsters, 8,085 +married bachelors, 627 married widowers, 1,221 were declined by +bachelors, and 231 declined by widowers. Of the 1,452 widows, 1,155 +married bachelors, and 297 married widowers. No widows were declined. +The problem is not difficult, by algebra, when once we have succeeded +in correctly stating it.</p> + +<hr style="width: 30%;" /> +<p><a name="X_109_THE_GREAT_SCRAMBLEa" id="X_109_THE_GREAT_SCRAMBLEa"></a><a href="#X_109_THE_GREAT_SCRAMBLE"><b>109.—THE GREAT SCRAMBLE.—<i>solution</i></b></a></p> + +<p>The smallest number of sugar plums that will fulfil the conditions is +26,880. The five boys obtained respectively: Andrew, 2,863; Bob, +6,335; Charlie, 2,438; David, 10,294; Edgar, 4,950. There is a +little trap concealed in the words near the end, "one-fifth of the +same," that seems at first sight to upset the whole account of the +affair. But a little thought will show that the words could only mean +"one-fifth of five-eighths", the fraction last mentioned—that is, +one-eighth of the three-quarters that Bob and Andrew had last +acquired.</p> + +<hr style="width: 30%;" /> +<p><a name="X_110_THE_ABBOTS_PUZZLEa" id="X_110_THE_ABBOTS_PUZZLEa"></a><a href="#X_110_THE_ABBOTS_PUZZLE"><b>110.—THE ABBOT'S PUZZLE.—<i>solution</i></b></a></p> + +<p>The only answer is that there were 5 men, 25 women, and 70 children. +There were thus 100 persons in all, 5 times as many women as men, and +as the men would together receive 15 bushels, the women 50 bushels, +and the children 35 bushels, exactly 100 bushels would be distributed.</p> + +<hr style="width: 30%;" /> +<p><a name="X_111_REAPING_THE_CORNa" id="X_111_REAPING_THE_CORNa"></a><a href="#X_111_REAPING_THE_CORN"><b>111.—REAPING THE CORN.—<i>solution</i></b></a></p> + +<p>The whole field must have contained 46.626 square rods. The side of +the central square, left by the farmer, is 4.8284 rods, so it contains +23.313 square rods. The area of the field was thus something more than +a quarter of an acre and less than one-third; to be more precise, +.2914 of an acre.</p> + +<hr style="width: 30%;" /> +<p><a name="X_112_A_PUZZLING_LEGACYa" id="X_112_A_PUZZLING_LEGACYa"></a><a href="#X_112_A_PUZZLING_LEGACY"><b>112.—A PUZZLING LEGACY.—<i>solution</i></b></a></p> + +<p>As the share of Charles falls in through his death, we have merely to +divide the whole hundred acres between Alfred and Benjamin in the +proportion of one-third to one-fourth—that is in the proportion of +four-twelfths to three-<span class='pagenum'>Pg 162<a name="Page_162" id="Page_162"></a></span>twelfths, which is the same as four to three. +Therefore Alfred takes four-sevenths of the hundred acres and Benjamin +three-sevenths.</p> + +<hr style="width: 30%;" /> +<p><a name="X_113_THE_TORN_NUMBERa" id="X_113_THE_TORN_NUMBERa"></a><a href="#X_113_THE_TORN_NUMBER"><b>113.—THE TORN NUMBER.—<i>solution</i></b></a></p> + +<p>The other number that answers all the requirements of the puzzle is +9,801. If we divide this in the middle into two numbers and add them +together we get 99, which, multiplied by itself, produces 9,801. It is +true that 2,025 may be treated in the same way, only this number is +excluded by the condition which requires that no two figures should be +alike.</p> + +<p>The general solution is curious. Call the number of figures in each +half of the torn label n. Then, if we add 1 to each of the exponents +of the prime factors (other than 3) of 10<sup>n</sup> - 1 (1 being regarded as a +factor with the constant exponent, 1), their product will be the +number of solutions. Thus, for a label of six figures, n = 3. The +factors of 10<sup>n</sup> - 1 are 1<sup>1</sup> × 37<sup>1</sup> (not considering the 3<sup>3</sup>), and the +product of 2 × 2 = 4, the number of solutions. This always includes +the special cases 98 - 01, 00 - 01, 998 - 01, 000 - 001, etc. The +solutions are obtained as follows:—Factorize 10<sup>3</sup> - 1 in all possible +ways, always keeping the powers of 3 together, thus, 37 × 27, 999 × 1. +Then solve the equation 37x = 27y + 1. Here x = 19 and y = 26. +Therefore, 19 × 37 = 703, the square of which gives one label, +494,209. A complementary solution (through 27x = 37x + 1) can at once +be found by 10<sup>n</sup> - 703 = 297, the square of which gives 088,209 for +second label. (These non-significant noughts to the left must be +included, though they lead to peculiar cases like 00238 - 04641 = +4879<sup>2</sup>, where 0238 - 4641 would not work.) The special case 999 × 1 we +can write at once 998,001, according to the law shown above, by adding +nines on one half and noughts on the other, and its complementary will +be 1 preceded by five noughts, or 000001. Thus we get the squares of +999 and 1. These are the four solutions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_114_CURIOUS_NUMBERSa" id="X_114_CURIOUS_NUMBERSa"></a><a href="#X_114_CURIOUS_NUMBERS"><b>114.—CURIOUS NUMBERS.—<i>solution</i></b></a></p> + +<p>The three smallest numbers, in addition to 48, are 1,680, 57,120, and +1,940,448. It will be found that 1,681 and 841, 57,121 and 28,561, +1,940,449 and 970,225, are respectively the squares of 41 and 29, 239 +and 169, 1,393 and 985.</p> + +<hr style="width: 30%;" /> +<p><a name="X_115_A_PRINTERS_ERRORa" id="X_115_A_PRINTERS_ERRORa"></a><a href="#X_115_A_PRINTERS_ERROR"><b>115.—A PRINTER'S ERROR.—<i>solution</i></b></a></p> + +<p>The answer is that 2<sup>5</sup> × 9<sup>2</sup> is the same as 2592, and this is the only +possible solution to the puzzle.</p> + +<hr style="width: 30%;" /> +<p><a name="X_116_THE_CONVERTED_MISERa" id="X_116_THE_CONVERTED_MISERa"></a><a href="#X_116_THE_CONVERTED_MISER"><b>116.—THE CONVERTED MISER.—<i>solution</i></b></a></p> + +<p>As we are not told in what year Mr. Jasper Bullyon made the generous +distribution of his accumulated wealth, but are required to find the +lowest possible amount of money, it is clear that we must look for a +year of the most favourable form.</p> + +<p>There are four cases to be considered—an ordinary year with fifty-two +Sundays and with fifty-three Sundays, and a leap-year with fifty-two +and fifty-three Sundays respectively. Here are the lowest possible +amounts in each case:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>313</td><td align='center'>weekdays,</td><td align='center'>52 Sundays</td><td align='center'>£112,055</td></tr> +<tr><td align='center'>312</td><td align='center'>weekdays,</td><td align='center'>53 Sundays</td><td align='center'>19,345</td></tr> +<tr><td align='center'>314</td><td align='center'>weekdays,</td><td align='center'>52 Sundays</td><td align='center'>No solution possible.</td></tr> +<tr><td align='center'>313</td><td align='center'>weekdays,</td><td align='center'>53 Sundays</td><td align='center'>£69,174</td></tr> +</table></div> + +<p>The lowest possible amount, and therefore the correct answer, is +£19,345, distributed in an ordinary year that began on a Sunday. The +last year of this kind was 1911. He would have paid £53 on every day +of the year, or £62 on every weekday, with £1 left over, as required, +in the latter event.</p> + +<hr style="width: 30%;" /> +<p><a name="X_117_A_FENCE_PROBLEMa" id="X_117_A_FENCE_PROBLEMa"></a><a href="#X_117_A_FENCE_PROBLEM"><b>117.—A FENCE PROBLEM.—<i>solution</i></b></a></p> + +<p>Though this puzzle presents no great difficulty to any one possessing +a knowledge of algebra, it has perhaps rather interesting features.</p> + +<p>Seeing, as one does in the illustration, just one corner of the +proposed square, one is scarcely prepared for the fact that the field, +in order to comply with the conditions, must contain exactly 501,760 +acres, the fence requiring the same number of rails. Yet this is the +correct answer, and the only answer, and if that gentleman in Iowa +carries out his intention, his field will be twenty-eight miles long +on each side, and a little larger than the county of Westmorland. I am +not aware that any limit has ever been fixed to the size of a "field," +though they do not run so large as this in Great Britain. Still, out +in Iowa, where my correspondent resides, they do these things on a +very big scale. I have, however, reason to believe that when he finds +the sort of task he has set himself, he will decide to abandon it; for +if that cow decides to roam to fresh woods and pastures new, the +milkmaid may have to start out a week in advance in order to obtain +the morning's milk.</p> + +<p>Here is a little rule that will always apply where the length of the +rail is half a pole. Multiply the number of rails in a hurdle by four, +and the result is the exact number of miles in the side of a square +field containing the same number of acres as there are rails in the +complete fence. Thus, with a one-rail fence the field is four miles +square; a two-rail fence gives eight miles square; a three-rail fence, +twelve miles square; and so on, until we find that a seven-rail fence +multiplied by four gives a field of twenty-eight miles square. In the +case of our present problem, if the field be made smaller, then the +number of rails will exceed the number of acres; while if the field be +made larger, the number of rails will be less than the acres of the +field.</p> + +<hr style="width: 30%;" /> +<p><a name="X_118_CIRCLING_THE_SQUARESa" id="X_118_CIRCLING_THE_SQUARESa"></a><a href="#X_118_CIRCLING_THE_SQUARES"><b>118.—CIRCLING THE SQUARES.—<i>solution</i></b></a></p> + +<p>Though this problem might strike the novice as being rather difficult, +it is, as a matter of fact, quite easy, and is made still easier by +inserting four out of the ten numbers.</p> + +<p><span class='pagenum'>Pg 163<a name="Page_163" id="Page_163"></a></span>First, it will be found that squares that are diametrically opposite +have a common difference. For example, the difference between the +square of 14 and the square of 2, in the diagram, is 192; and the +difference between the square of 16 and the square of 8 is also 192. +This must be so in every case. Then it should be remembered that the +difference between squares of two consecutive numbers is always twice +the smaller number plus 1, and that the difference between the squares +of any two numbers can always be expressed as the difference of the +numbers multiplied by their sum. Thus the square of 5 (25) less the +square of 4 (16) equals (2 × 4) + 1, or 9; also, the square of 7 (49) +less the square of 3 (9) equals (7 + 3) × (7 - 3), or 40.</p> + +<p>Now, the number 192, referred to above, may be divided into five +different pairs of even factors: 2 × 96, 4 × 48, 6 × 32, 8 × 24, and +12 × 16, and these divided by 2 give us, 1 × 48, 2 × 24, 3 × 16, 4 × +12, and 6 × 8. The difference and sum respectively of each of these +pairs in turn produce 47, 49; 22, 26; 13, 19; 8, 16; and 2, 14. These +are the required numbers, four of which are already placed. The six +numbers that have to be added may be placed in just six different +ways, one of which is as follows, reading round the circle clockwise: +16, 2, 49, 22, 19, 8, 14, 47, 26, 13.</p> + +<p>I will just draw the reader's attention to one other little point. In +all circles of this kind, the difference between diametrically +opposite numbers increases by a certain ratio, the first numbers (with +the exception of a circle of 6) being 4 and 6, and the others formed +by doubling the next preceding but one. Thus, in the above case, the +first difference is 2, and then the numbers increase by 4, 6, 8, and +12. Of course, an infinite number of solutions may be found if we +admit fractions. The number of squares in a circle of this kind must, +however, be of the form 4n + 6; that is, it must be a number composed +of 6 plus a multiple of 4.</p> + +<hr style="width: 30%;" /> +<p><a name="X_119_RACKBRANES_LITTLE_LOSSa" id="X_119_RACKBRANES_LITTLE_LOSSa"></a><a href="#X_119_RACKBRANES_LITTLE_LOSS"><b>119.—RACKBRANE'S LITTLE LOSS.—<i>solution</i></b></a></p> + +<p>The professor must have started the game with thirteen shillings, Mr. +Potts with four shillings, and Mrs. Potts with seven shillings.</p> + +<hr style="width: 30%;" /> +<p><a name="X_120_THE_FARMER_AND_HIS_SHEEPa" id="X_120_THE_FARMER_AND_HIS_SHEEPa"></a><a href="#X_120_THE_FARMER_AND_HIS_SHEEP"><b>120.—THE FARMER AND HIS SHEEP.—<i>solution</i></b></a></p> + +<p>The farmer had one sheep only! If he divided this sheep (which is best +done by weight) into two parts, making one part two-thirds and the +other part one-third, then the difference between these two numbers is +the same as the difference between their squares—that is, one-third. +Any two fractions will do if the denominator equals the sum of the two +numerators.</p> + +<hr style="width: 30%;" /> +<p><a name="X_121_HEADS_OR_TAILSa" id="X_121_HEADS_OR_TAILSa"></a><a href="#X_121_HEADS_OR_TAILS"><b>121.—HEADS OR TAILS.—<i>solution</i></b></a></p> + +<p>Crooks must have lost, and the longer he went on the more he would +lose. In two tosses he would be left with three-quarters of his money, +in four tosses with nine-sixteenths of his money, in six tosses with +twenty-seven sixty-fourths of his money, and so on. The order of the +wins and losses makes no difference, so long as their number is in the +end equal.</p> + +<hr style="width: 30%;" /> +<p><a name="X_122_THE_SEE-SAW_PUZZLEa" id="X_122_THE_SEE-SAW_PUZZLEa"></a><a href="#X_122_THE_SEE-SAW_PUZZLE"><b>122.—THE SEE-SAW PUZZLE.—<i>solution</i></b></a></p> + +<p>The boy's weight must have been about 39.79 lbs. A brick weighed 3 +lbs. Therefore 16 bricks weighed 48 lbs. and 11 bricks 33 lbs. +Multiply 48 by 33 and take the square root.</p> + +<hr style="width: 30%;" /> +<p><a name="X_123_A_LEGAL_DIFFICULTYa" id="X_123_A_LEGAL_DIFFICULTYa"></a><a href="#X_123_A_LEGAL_DIFFICULTY"><b>123.—A LEGAL DIFFICULTY.—<i>solution</i></b></a></p> + +<p>It was clearly the intention of the deceased to give the son twice as +much as the mother, or the daughter half as much as the mother. +Therefore the most equitable division would be that the mother should +take two-sevenths, the son four-sevenths, and the daughter +one-seventh.</p> + +<hr style="width: 30%;" /> +<p><a name="X_124_A_QUESTION_OF_DEFINITIONa" id="X_124_A_QUESTION_OF_DEFINITIONa"></a><a href="#X_124_A_QUESTION_OF_DEFINITION"><b>124.—A QUESTION OF DEFINITION.—<i>solution</i></b></a></p> + +<p>There is, of course, no difference in <i>area</i> between a mile square and +a square mile. But there may be considerable difference in <i>shape</i>. A +mile square can be no other shape than square; the expression +describes a surface of a certain specific size and shape. A square +mile may be of any shape; the expression names a unit of area, but +does not prescribe any particular shape.</p> + +<hr style="width: 30%;" /> +<p><a name="X_125_THE_MINERS_HOLIDAYa" id="X_125_THE_MINERS_HOLIDAYa"></a><a href="#X_125_THE_MINERS_HOLIDAY"><b>125.—THE MINERS' HOLIDAY.—<i>solution</i></b></a></p> + +<p>Bill Harris must have spent thirteen shillings and sixpence, which +would be three shillings more than the average for the seven men—half +a guinea.</p> + +<hr style="width: 30%;" /> +<p><a name="X_126_SIMPLE_MULTIPLICATIONa" id="X_126_SIMPLE_MULTIPLICATIONa"></a><a href="#X_126_SIMPLE_MULTIPLICATION"><b>126.—SIMPLE MULTIPLICATION.—<i>solution</i></b></a></p> + +<p>The number required is 3,529,411,764,705,882, which may be multiplied +by 3 and divided by 2, by the simple expedient of removing the 3 from +one end of the row to the other. If you want a longer number, you can +increase this one to any extent by repeating the sixteen figures in +the same order.</p> + +<hr style="width: 30%;" /> +<p><a name="X_127_SIMPLE_DIVISIONa" id="X_127_SIMPLE_DIVISIONa"></a><a href="#X_127_SIMPLE_DIVISION"><b>127.—SIMPLE DIVISION.—<i>solution</i></b></a></p> + +<p>Subtract every number in turn from every other number, and we get 358 +(twice), 716, 1,611, 1,253, and 895. Now, we see at a glance that, as +358 equals 2 × 179, the only number that can divide in every case +without a remainder will be 179. On trial we find that this is such a +divisor. Therefore, 179 is the divisor we want, which always leaves a +remainder 164 in the case of the original numbers given.</p> + +<hr style="width: 30%;" /> +<p><a name="X_128_A_PROBLEM_IN_SQUARESa" id="X_128_A_PROBLEM_IN_SQUARESa"></a><a href="#X_128_A_PROBLEM_IN_SQUARES"><b>128.—A PROBLEM IN SQUARES.—<i>solution</i></b></a></p> + +<p>The sides of the three boards measure 31 in., 41 in., and 49 in. The +common difference of area is exactly five square feet. Three numbers +whose squares are in A.P., with a common difference of 7, are <sup>113</sup>/<sub>120</sub>, +<sup>337</sup>/<sub>120</sub>, <sup>463</sup>/<sub>120</sub>; and with <span class='pagenum'>Pg 164<a name="Page_164" id="Page_164"></a></span>a common difference of 13 are <sup>80929</sup>/<sub>19380</sub>, +<sup>106921</sup>/<sub>19380</sub>, and <sup>127729</sup>/<sub>19380</sub>. In the case of whole square numbers +the common difference will always be divisible by 24, so it is obvious +that our squares must be fractional. Readers should now try to solve +the case where the common difference is 23. It is rather a hard nut.</p> + +<hr style="width: 30%;" /> +<p><a name="X_129_THE_BATTLE_OF_HASTINGSa" id="X_129_THE_BATTLE_OF_HASTINGSa"></a><a href="#X_129_THE_BATTLE_OF_HASTINGS"><b>129.—THE BATTLE OF HASTINGS.—<i>solution</i></b></a></p> + +<p>Any number (not itself a square number) may be multiplied by a square +that will give a product 1 less than another square. The given number +must not itself be a square, because a square multiplied by a square +produces a square, and no square plus 1 can be a square. My remarks +throughout must be understood to apply to whole numbers, because +fractional soldiers are not of much use in war.</p> + +<p>Now, of all the numbers from 2 to 99 inclusive, 61 happens to be the +most awkward one to work, and the lowest possible answer to our puzzle +is that Harold's army consisted of 3,119,882,982,860,264,400 men. That +is, there would be 51,145,622,669,840,400 men (the square of +226,153,980) in each of the sixty-one squares. Add one man (Harold), +and they could then form one large square with 1,766,319,049 men on +every side. The general problem, of which this is a particular case, +is known as the "Pellian Equation"—apparently because Pell neither +first propounded the question nor first solved it! It was issued as a +challenge by Fermat to the English mathematicians of his day. It is +readily solved by the use of continued fractions.</p> + +<p>Next to 61, the most difficult number under 100 is 97, where +97 × 6,377,352<sup>2</sup> + 1 = a square.</p> + +<p>The reason why I assumed that there must be something wrong with the +figures in the chronicle is that we can confidently say that Harold's +army did not contain over three trillion men! If this army (not to +mention the Normans) had had the whole surface of the earth (sea +included) on which to encamp, each man would have had slightly more +than a quarter of a square inch of space in which to move about! Put +another way: Allowing one square foot of standing-room per man, each +small square would have required all the space allowed by a globe +three times the diameter of the earth.</p> + +<hr style="width: 30%;" /> +<p><a name="X_130_THE_SCULPTORS_PROBLEMa" id="X_130_THE_SCULPTORS_PROBLEMa"></a><a href="#X_130_THE_SCULPTORS_PROBLEM"><b>130.—THE SCULPTOR'S PROBLEM.—<i>solution</i></b></a></p> + +<p>A little thought will make it clear that the answer must be +fractional, and that in one case the numerator will be greater and in +the other case less than the denominator. As a matter of fact, the +height of the larger cube must be <sup>8</sup>/<sub>7</sub> ft., and of the smaller <sup>3</sup>/<sub>7</sub> ft., +if we are to have the answer in the smallest possible figures. Here +the lineal measurement is <sup>11</sup>/<sub>7</sub> ft.—that is, 1<sup>4</sup>/<sub>7</sub> ft. What are the +cubic contents of the two cubes? First <sup>8</sup>/<sub>7</sub> × <sup>3</sup>/<sub>7</sub> × <sup>8</sup>/<sub>7</sub> = <sup>512</sup>/<sub>343</sub>, and +secondly <sup>3</sup>/<sub>7</sub> × <sup>3</sup>/<sub>7</sub> × <sup>3</sup>/<sub>7</sub> = <sup>27</sup>/<sub>343</sub>. Add these together and the result +is <sup>539</sup>/<sub>343</sub>, which reduces to <sup>11</sup>/<sub>7</sub> or 1<sup>4</sup>/<sub>7</sub> ft. We thus see that the +answers in cubic feet and lineal feet are precisely the same.</p> + +<p>The germ of the idea is to be found in the works of Diophantus of +Alexandria, who wrote about the beginning of the fourth century. These +fractional numbers appear in triads, and are obtained from three +generators, <i>a</i>, <i>b</i>, <i>c</i>, where <i>a</i> is the largest and <i>c</i> the +smallest.</p> + +<p>Then <i>ab</i>+<i>c</i><sup>2</sup>=denominator, and <i>a</i><sup>2</sup>-<i>c</i><sup>2</sup>, <i>b</i><sup>2</sup>-<i>c</i><sup>2</sup>, +and <i>a</i><sup>2</sup>-<i>b</i><sup>2</sup> will be the three numerators. Thus, using the +generators 3, 2, 1, we get <sup>8</sup>/<sub>7</sub>, <sup>3</sup>/<sub>7</sub>, <sup>5</sup>/<sub>7</sub> and we can pair the first and +second, as in the above solution, or the first and third for a second +solution. The denominator must always be a prime number of the form +6<i>n</i>+1, or composed of such primes. Thus you can have 13, 19, etc., as +denominators, but not 25, 55, 187, etc.</p> + +<p>When the principle is understood there is no difficulty in writing +down the dimensions of as many sets of cubes as the most exacting +collector may require. If the reader would like one, for example, with +plenty of nines, perhaps the following would satisfy him: +<sup>99999999</sup>/<sub>99990001</sub> and <sup>19999</sup>/<sub>99990001</sub>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_131_THE_SPANISH_MISERa" id="X_131_THE_SPANISH_MISERa"></a><a href="#X_131_THE_SPANISH_MISER"><b>131.—THE SPANISH MISER.—<i>solution</i></b></a></p> + +<p>There must have been 386 doubloons in one box, 8,450 in another, and +16,514 in the third, because 386 is the smallest number that can +occur. If I had asked for the smallest aggregate number of coins, the +answer would have been 482, 3,362, and 6,242. It will be found in +either case that if the contents of any two of the three boxes be +combined, they form a square number of coins. It is a curious +coincidence (nothing more, for it will not always happen) that in the +first solution the digits of the three numbers add to 17 in every +case, and in the second solution to 14. It should be noted that the +middle one of the three numbers will always be half a square.</p> + +<hr style="width: 30%;" /> +<p><a name="X_132_THE_NINE_TREASURE_BOXESa" id="X_132_THE_NINE_TREASURE_BOXESa"></a><a href="#X_132_THE_NINE_TREASURE_BOXES"><b>132.—THE NINE TREASURE BOXES.—<i>solution</i></b></a></p> + +<p>Here is the answer that fulfils the conditions:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>A = 4</td><td align='left'>B = 3,364</td><td align='left'>C = 6,724</td></tr> +<tr><td align='left'>D = 2,116</td><td align='left'>E = 5,476</td><td align='left'>F = 8,836</td></tr> +<tr><td align='left'>G = 9,409</td><td align='left'>H = 12,769</td><td align='left'>I = 16,129</td></tr> +</table></div> + + +<p>Each of these is a square number, the roots, taken in alphabetical +order, being 2, 58, 82, 46, 74, 94, 97, 113, and 127, while the +required difference between A and B, B and C, D and E. etc., is in +every case 3,360.</p> + +<hr style="width: 30%;" /> +<p><a name="X_133_THE_FIVE_BRIGANDSa" id="X_133_THE_FIVE_BRIGANDSa"></a><a href="#X_133_THE_FIVE_BRIGANDS"><b>133.—THE FIVE BRIGANDS.—<i>solution</i></b></a></p> + +<p>The sum of 200 doubloons might have been held by the five brigands in +any one of 6,627 different ways. Alfonso may have held any number from +1 to 11. If he held 1 doubloon, there are 1,005 different ways of +distributing the remainder; if he held 2, there are 985 ways; if 3, +there are 977 ways; if 4, there are 903 ways; if 5 doubloons, 832 +ways; if 6 doubloons, 704 ways; if 7 doubloons, 570 ways; if 8 +doubloons, 388 ways; if 9 doubloons, 200 ways; if 10 doubloons, 60 +ways; and if Alfonso held 11 doubloons, the remainder could be +distri<span class='pagenum'>Pg 165<a name="Page_165" id="Page_165"></a></span>buted in 3 different ways. More than 11 doubloons he could not +possibly have had. It will scarcely be expected that I shall give all +these 6,627 ways at length. What I propose to do is to enable the +reader, if he should feel so disposed, to write out all the answers +where Alfonso has one and the same amount. Let us take the cases where +Alfonso has 6 doubloons, and see how we may obtain all the 704 +different ways indicated above. Here are two tables that will serve as +keys to all these answers:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' colspan='3'>Table I.</td></tr> +<tr><td align='center'>A</td><td align='center'>=</td><td align='left'>6.</td></tr> +<tr><td align='center'>B</td><td align='center'>=</td><td align='left'>n.</td></tr> +<tr><td align='center'>C</td><td align='center'>=</td><td align='left'>(63 - 5n) + m.</td></tr> +<tr><td align='center'>D</td><td align='center'>=</td><td align='left'>(128 + 4n) - 4m.</td></tr> +<tr><td align='center'>E</td><td align='center'>=</td><td align='left'>3 + 3m.</td></tr> +</table><br /><br /></div> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' colspan='3'>Table II.</td></tr> +<tr><td align='center'>A</td><td align='center'>=</td><td align='left'>6.</td></tr> +<tr><td align='center'>B</td><td align='center'>=</td><td align='left'>n.</td></tr> +<tr><td align='center'>C</td><td align='center'>=</td><td align='left'>1 + m.</td></tr> +<tr><td align='center'>D</td><td align='center'>=</td><td align='left'>(376 - 16n) - 4m.</td></tr> +<tr><td align='center'>E</td><td align='center'>=</td><td align='left'>(15n - 183) + 3m.</td></tr> +</table></div> + +<p>In the first table we may substitute for n any whole number from 1 to +12 inclusive, and m may be nought or any whole number from 1 to (31 + +n) inclusive. In the second table n may have the value of any whole +number from 13 to 23 inclusive, and m may be nought or any whole +number from 1 to (93 - 4n) inclusive. The first table thus gives (32 + +n) answers for every value of n; and the second table gives (94 - 4n) +answers for every value of n. The former, therefore, produces 462 and +the latter 242 answers, which together make 704, as already stated.</p> + +<p>Let us take Table I., and say n = 5 and m = 2; also in Table II. take +n = 13 and m = 0. Then we at once get these two answers:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' colspan='3'>Table I.</td></tr> +<tr><td align='center'>A</td><td align='center'>=</td><td align='right'>6</td></tr> +<tr><td align='center'>B</td><td align='center'>=</td><td align='right'>5</td></tr> +<tr><td align='center'>C</td><td align='center'>=</td><td align='right'>40</td></tr> +<tr><td align='center'>D</td><td align='center'>=</td><td align='right'>140</td></tr> +<tr><td align='center'>E</td><td align='center'>=</td><td align='right' class='bb'>9</td></tr> +<tr><td align='center'></td><td></td><td align='right'>200 <br />doubloons</td></tr> +</table><br /><br /></div> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' colspan='3'>Table II.</td></tr> +<tr><td align='center'>A</td><td align='center'>=</td><td align='right'>6</td></tr> +<tr><td align='center'>B</td><td align='center'>=</td><td align='right'>13</td></tr> +<tr><td align='center'>C</td><td align='center'>=</td><td align='right'>1</td></tr> +<tr><td align='center'>D</td><td align='center'>=</td><td align='right'>168</td></tr> +<tr><td align='center'>E</td><td align='center'>=</td><td align='right' class='bb'>12</td></tr> +<tr><td align='center'></td><td></td><td align='right'>200 <br />doubloons.</td></tr> +</table></div> + +<p>These will be found to work correctly. All the rest of the 704 +answers, where Alfonso always holds six doubloons, may be obtained in +this way from the two tables by substituting the different numbers for +the letters m and n.</p> + +<p>Put in another way, for every holding of Alfonso the number of answers +is the sum of two arithmetical progressions, the common difference in +one case being 1 and in the other -4. Thus in the case where Alfonso +holds 6 doubloons one progression is 33 + 34 + 35 + 36 + ... + 43 + +44, and the other 42 + 38 + 34 + 30 + ... + 6 + 2. The sum of the +first series is 462, and of the second 242—results which again agree +with the figures already given. The problem may be said to consist in +finding the first and last terms of these progressions. I should +remark that where Alfonso holds 9, 10, or 11 there is only one +progression, of the second form.</p> + +<hr style="width: 30%;" /> +<p><a name="X_134_THE_BANKERS_PUZZLEa" id="X_134_THE_BANKERS_PUZZLEa"></a><a href="#X_134_THE_BANKERS_PUZZLE"><b>134.—THE BANKER'S PUZZLE.—<i>solution</i></b></a></p> + +<p>In order that a number of sixpences may not be divisible into a number +of equal piles, it is necessary that the number should be a prime. If +the banker can bring about a prime number, he will win; and I will +show how he can always do this, whatever the customer may put in the +box, and that therefore the banker will win to a certainty. The banker +must first deposit forty sixpences, and then, no matter how many the +customer may add, he will desire the latter to transfer from the +counter the square of the number next below what the customer put in. +Thus, banker puts 40, customer, we will say, adds 6, then transfers +from the counter 25 (the square of 5), which leaves 71 in all, a prime +number. Try again. Banker puts 40, customer adds 12, then transfers +121 (the square of 11), as desired, which leaves 173, a prime number. +The key to the puzzle is the curious fact that any number up to 39, if +added to its square and the sum increased by 41, makes a prime number. +This was first discovered by Euler, the great mathematician. It has +been suggested that the banker might desire the customer to transfer +sufficient to raise the contents of the box to a given number; but +this would not only make the thing an absurdity, but breaks the rule +that neither knows what the other puts in.</p> + +<hr style="width: 30%;" /> +<p><a name="X_135_THE_STONEMASONS_PROBLEMa" id="X_135_THE_STONEMASONS_PROBLEMa"></a><a href="#X_135_THE_STONEMASONS_PROBLEM"><b>135.—THE STONEMASON'S PROBLEM.—<i>solution</i></b></a></p> + +<p>The puzzle amounts to this. Find the smallest square number that may +be expressed as the sum of more than three consecutive cubes, the cube +1 being barred. As more than three heaps were to be supplied, this +condition shuts out the otherwise smallest answer, 23<sup>3</sup> + 24<sup>3</sup> + 25<sup>3</sup> += 204<sup>2</sup>. But it admits the answer, 25<sup>3</sup> + 26<sup>3</sup> + 27<sup>3</sup> + 28<sup>3</sup> + 29<sup>3</sup> = +315<sup>2</sup>. The correct answer, however, requires more heaps, but a smaller +aggregate number of blocks. Here it is: 14<sup>3</sup> + 15<sup>3</sup> + ... up to 25<sup>3</sup> +inclusive, or twelve heaps in all, which, added together, make 97,344 +blocks of stone that may be laid out to form a square 312 × 312. I +will just remark that one key to the solution lies in what are called +triangular numbers. (See pp. <a href="#Page_13">13</a>, <a href="#Page_25">25</a>, and <a href="#Page_166">166</a>.)</p> + +<hr style="width: 30%;" /> +<p><a name="X_136_THE_SULTANS_ARMYa" id="X_136_THE_SULTANS_ARMYa"></a><a href="#X_136_THE_SULTANS_ARMY"><b>136.—THE SULTAN'S ARMY.—<i>solution</i></b></a></p> + +<p>The smallest primes of the form 4n + 1 are 5, 13, 17, 29, and 37, and +the smallest of the form 4n - 1 are 3, 7, 11, 19, and 23. Now, primes +of the first form can always be expressed as the sum of two squares, +and in only one way. Thus, 5 = 4 + 1; 13 = 9 + 4; 17 = 16 + 1; 29 = 25 ++ 4; 37 = 36 + 1. But primes of the second form can never be +expressed as the sum of two squares in any way whatever.</p> + +<p>In order that a number may be expressed as the sum of two squares in +several different ways, it is necessary that it shall be a composite +number containing a certain number of primes of our first form. Thus, +5 or 13 alone can only be so expressed in one way; but 65, (5 × 13), +can be expressed in two ways, 1,105, (5 × 13 × 17), in four ways, +32,045, (5 × 13 × 17 × 29), in eight ways. We thus get double as many +ways for every new factor of this form that we introduce. Note, +however, that I say <i>new</i> <span class='pagenum'>Pg 166<a name="Page_166" id="Page_166"></a></span>factor, for the <i>repetition</i> of factors is +subject to another law. We cannot express 25, (5 × 5), in two ways, +but only in one; yet 125, (5 × 5 × 5), can be given in two ways, and +so can 625, (5 × 5 × 5 × 5); while if we take in yet another 5 we can +express the number as the sum of two squares in three different ways.</p> + +<p>If a prime of the second form gets into your composite number, then +that number cannot be the sum of two squares. Thus 15, (3 × 5), will +not work, nor will 135, (3 × 3 × 3 × 5); but if we take in an even +number of 3's it will work, because these 3's will themselves form a +square number, but you will only get one solution. Thus, 45, (3 × 3 × +5, or 9 × 5) = 36 + 9. Similarly, the factor 2 may always occur, or +any power of 2, such as 4, 8, 16, 32; but its introduction or omission +will never affect the number of your solutions, except in such a case +as 50, where it doubles a square and therefore gives you the two +answers, 49 + 1 and 25 + 25.</p> + +<p>Now, directly a number is decomposed into its prime factors, it is +possible to tell at a glance whether or not it can be split into two +squares; and if it can be, the process of discovery in how many ways +is so simple that it can be done in the head without any effort. The +number I gave was 130. I at once saw that this was 2 × 5 × 13, and +consequently that, as 65 can be expressed in two ways (64 + 1 and 49 + +16), 130 can also be expressed in two ways, the factor 2 not affecting +the question.</p> + +<p>The smallest number that can be expressed as the sum of two squares in +twelve different ways is 160,225, and this is therefore the smallest +army that would answer the Sultan's purpose. The number is composed of +the factors 5 × 5 × 13 × 17 × 29, each of which is of the required +form. If they were all different factors, there would be sixteen ways; +but as one of the factors is repeated, there are just twelve ways. +Here are the sides of the twelve pairs of squares: (400 and 15), (399 +and 32), (393 and 76), (392 and 81), (384 and 113), (375 and 140), +(360 and 175), (356 and 183), (337 and 216), (329 and 228), (311 and +252), (265 and 300). Square the two numbers in each pair, add them +together, and their sum will in every case be 160,225.</p> + +<hr style="width: 30%;" /> +<p><a name="X_137_A_STUDY_IN_THRIFTa" id="X_137_A_STUDY_IN_THRIFTa"></a><a href="#X_137_A_STUDY_IN_THRIFT"><b>137.—A STUDY IN THRIFT.—<i>solution</i></b></a></p> + +<p>Mrs. Sandy McAllister will have to save a tremendous sum out of her +housekeeping allowance if she is to win that sixth present that her +canny husband promised her. And the allowance must be a very liberal +one if it is to admit of such savings. The problem required that we +should find five numbers higher than 36 the units of which may be +displayed so as to form a square, a triangle, two triangles, and three +triangles, using the complete number in every one of the four cases.</p> + +<p>Every triangular number is such that if we multiply it by 8 and add 1 +the result is an odd square number. For example, multiply 1, 3, 6, 10, +15 respectively by 8 and add 1, and we get 9, 25, 49, 81, 121, which +are the squares of the odd numbers 3, 5, 7, 9, 11. Therefore in every +case where 8x<sup>2</sup> + 1 = a square number, x<sup>2</sup> is also a triangular. This +point is dealt with in our puzzle, "The Battle of Hastings." I will +now merely show again how, when the first solution is found, the +others may be discovered without any difficulty. First of all, here +are the figures:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>8</td><td align='center'>×</td><td align='right'>1<sup>2</sup></td><td align='center'>+ 1 =</td><td align='right'>3<sup>2</sup></td></tr> +<tr><td align='center'>8</td><td align='center'>×</td><td align='right'>6<sup>2</sup></td><td align='center'>+ 1 =</td><td align='right'>17<sup>2</sup></td></tr> +<tr><td align='center'>8</td><td align='center'>×</td><td align='right'>35<sup>2</sup></td><td align='center'>+ 1 =</td><td align='right'>99<sup>2</sup></td></tr> +<tr><td align='center'>8</td><td align='center'>×</td><td align='right'>204<sup>2</sup></td><td align='center'>+ 1 =</td><td align='right'>577<sup>2</sup></td></tr> +<tr><td align='center'>8</td><td align='center'>×</td><td align='right'>1189<sup>2</sup></td><td align='center'>+ 1 =</td><td align='right'>3363<sup>2</sup></td></tr> +<tr><td align='center'>8</td><td align='center'>×</td><td align='right'>6930<sup>2</sup></td><td align='center'>+ 1 =</td><td align='right'>19601<sup>2</sup></td></tr> +<tr><td align='center'>8</td><td align='center'>×</td><td align='right'>40391<sup>2</sup></td><td align='center'>+ 1 =</td><td align='right'>114243<sup>2</sup></td></tr> +</table></div> + +<p>The successive pairs of numbers are found in this way:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>(1 × 3) + (3 × 1)</td><td align='center'>=</td><td align='right'>6</td><td> </td><td align='center'>(8 × 1) + (3 × 3)</td><td align='right'>=</td><td align='right'>17</td></tr> +<tr><td align='right'>(1 × 17) + (3 × 6)</td><td align='center'>=</td><td align='right'>35</td><td> </td><td align='center'>(8 × 6) + (3 × 17)</td><td align='right'>=</td><td align='right'>99</td></tr> +<tr><td align='right'>(1 × 99) + (3 × 35)</td><td align='center'>=</td><td align='right'>204</td><td> </td><td align='center'>(8 × 35) + (3 × 99)</td><td align='right'>=</td><td align='right'>577</td></tr> +</table></div> + +<p>and so on. Look for the numbers in the table above, and the method +will explain itself.</p> + +<p>Thus we find that the numbers 36, 1225, 41616, 1413721, 48024900, and +1631432881 will form squares with sides of 6, 35, 204, 1189, 6930, and +40391; and they will also form single triangles with sides of 8, 49, +288, 1681, 9800, and 57121. These numbers may be obtained from the +last column in the first table above in this way: simply divide the +numbers by 2 and reject the remainder. Thus the integral halves of 17, +99, and 577 are 8, 49, and 288.</p> + +<p>All the numbers we have found will form either two or three triangles +at will. The following little diagram will show you graphically at a +glance that every square number must necessarily be the sum of two +triangulars, and that the side of one triangle will be the same as the +side of the corresponding square, while the other will be just 1 less.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a137.png" width="400" height="206" alt="" title="" /> +</div> + +<p>Thus a square may always be divided easily into two triangles, and the +sum of two consecutive triangulars will always make a square. In +numbers it is equally clear, for if we examine the first +triangulars—1, 3, 6, 10, 15, 21, 28—we find that by adding all the +consecutive pairs in turn we get the series of square numbers—9, 16, +25, 36, 49, etc.</p> + +<p>The method of forming three triangles from our numbers is equally +direct, and not at all a matter of trial. But I must content myself +with giving actual figures, and just stating that every triangular +higher than 6 will form three triangulars. I give the sides of the +triangles, and readers will know from my remarks when stat<span class='pagenum'>Pg 167<a name="Page_167" id="Page_167"></a></span>ing the +puzzle how to find from these sides the number of counters or coins in +each, and so check the results if they so wish.</p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>Number</td><td align='right'>Side of <br />Square.</td><td align='center'>Side of <br />Triangle.</td><td align='center'>Sides of <br />Two Triangles.</td><td align='center'>Sides of <br />Three Triangles.</td></tr> +<tr><td align='right'>36</td><td align='right'>6</td><td align='center'>8</td><td align='center'>6 + 5</td><td align='center'>5 + 5 + 3</td></tr> +<tr><td align='right'>1225</td><td align='right'>35</td><td align='center'>49</td><td align='center'>36 + 34</td><td align='center'>33 + 32 + 16</td></tr> +<tr><td align='right'>41616</td><td align='right'>204</td><td align='center'>288</td><td align='center'>204 + 203</td><td align='center'>192 + 192 + 95</td></tr> +<tr><td align='right'>1413721</td><td align='right'>1189</td><td align='center'>1681</td><td align='center'>1189 + 1188</td><td align='center'>1121 + 1120 + 560</td></tr> +<tr><td align='right'>48024900</td><td align='right'>6930</td><td align='center'>9800</td><td align='center'>6930 + 6929</td><td align='center'>6533 + 6533 + 3267</td></tr> +<tr><td align='right'>1631432881</td><td align='right'>40391</td><td align='center'>57121</td><td align='center'>40391 + 40390</td><td align='center'>38081 + 38080 + 19040</td></tr> +</table></div> + +<p>I should perhaps explain that the arrangements given in the last two +columns are not the only ways of forming two and three triangles. +There are others, but one set of figures will fully serve our purpose. +We thus see that before Mrs. McAllister can claim her sixth £5 present +she must save the respectable sum of £1,631,432,881.</p> + +<hr style="width: 30%;" /> +<p><a name="X_138_THE_ARTILLERYMENS_DILEMMAa" id="X_138_THE_ARTILLERYMENS_DILEMMAa"></a><a href="#X_138_THE_ARTILLERYMENS_DILEMMA"><b>138.—THE ARTILLERYMEN'S DILEMMA.—<i>solution</i></b></a></p> + +<p>We were required to find the smallest number of cannon balls that we +could lay on the ground to form a perfect square, and could pile into +a square pyramid. I will try to make the matter clear to the merest +novice.</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>1</td><td align='right'>2</td><td align='right'>3</td><td align='right'>4</td><td align='right'>5</td><td align='right'>6</td><td align='right'>7</td></tr> +<tr><td align='right'>1</td><td align='right'>3</td><td align='right'>6</td><td align='right'>10</td><td align='right'>15</td><td align='right'>21</td><td align='right'>28</td></tr> +<tr><td align='right'>1</td><td align='right'>4</td><td align='right'>10</td><td align='right'>20</td><td align='right'>35</td><td align='right'>56</td><td align='right'>84</td></tr> +<tr><td align='right'>1</td><td align='right'>5</td><td align='right'>14</td><td align='right'>30</td><td align='right'>55</td><td align='right'>91</td><td align='right'>140</td></tr> +</table></div> + +<p>Here in the first row we place in regular order the natural numbers. +Each number in the second row represents the sum of the numbers in the +row above, from the beginning to the number just over it. Thus 1, 2, +3, 4, added together, make 10. The third row is formed in exactly the +same way as the second. In the fourth row every number is formed by +adding together the number just above it and the preceding number. +Thus 4 and 10 make 14, 20 and 35 make 55. Now, all the numbers in the +second row are triangular numbers, which means that these numbers of +cannon balls may be laid out on the ground so as to form equilateral +triangles. The numbers in the third row will all form our triangular +pyramids, while the numbers in the fourth row will all form square +pyramids.</p> + +<p>Thus the very process of forming the above numbers shows us that every +square pyramid is the sum of two triangular pyramids, one of which has +the same number of balls in the side at the base, and the other one +ball fewer. If we continue the above table to twenty-four places, we +shall reach the number 4,900 in the fourth row. As this number is the +square of 70, we can lay out the balls in a square, and can form a +square pyramid with them. This manner of writing out the series until +we come to a square number does not appeal to the mathematical mind, +but it serves to show how the answer to the particular puzzle may be +easily arrived at by anybody. As a matter of fact, I confess my +failure to discover any number other than 4,900 that fulfils the +conditions, nor have I found any rigid proof that this is the only +answer. The problem is a difficult one, and the second answer, if it +exists (which I do not believe), certainly runs into big figures.</p> + +<p>For the benefit of more advanced mathematicians I will add that the +general expression for square pyramid numbers is (2n<sup>3</sup> + 3n<sup>2</sup> + n)/6. +For this expression to be also a square number (the special case of 1 +excepted) it is necessary that n = p<sup>2</sup> - 1 = 6t<sup>2</sup>, where 2p<sup>2</sup> - 1 = +q<sup>2</sup> (the "Pellian Equation"). In the case of our solution above, n = +24, p = 5, t = 2, q = 7.</p> + +<hr style="width: 30%;" /> +<p><a name="X_139_THE_DUTCHMENS_WIVESa" id="X_139_THE_DUTCHMENS_WIVESa"></a><a href="#X_139_THE_DUTCHMENS_WIVES"><b>139.—THE DUTCHMEN'S WIVES.—<i>solution</i></b></a></p> + +<p>The money paid in every case was a square number of shillings, because +they bought 1 at 1<i>s</i>., 2 at 2<i>s</i>., 3 at 3<i>s</i>., and so on. But every husband +pays altogether 63<i>s</i>. more than his wife, so we have to find in how +many ways 63 may be the difference between two square numbers. These +are the three only possible ways: the square of 8 less the square of +1, the square of 12 less the square of 9, and the square of 32 less +the square of 31. Here 1, 9, and 31 represent the number of pigs +bought and the number of shillings per pig paid by each woman, and 8, +12, and 32 the same in the case of their respective husbands. From the +further information given as to their purchases, we can now pair them +off as follows: Cornelius and Gurtrün bought 8 and 1; Elas and Katrün +bought 12 and 9; Hendrick and Anna bought 32 and 31. And these pairs +represent correctly the three married couples.</p> + +<p>The reader may here desire to know how we may determine the maximum +number of ways in which a number may be expressed as the difference +between two squares, and how we are to find the actual squares. Any +integer except 1, 4, and twice any odd number, may be expressed as the +difference of two integral squares in as many ways as it can be split +up into pairs of factors, counting 1 as a factor. Suppose the number +to be 5,940. The factors are <span class='pagenum'>Pg 168<a name="Page_168" id="Page_168"></a></span>2<sup>2</sup>.3<sup>3</sup>.5.11. Here the exponents are 2, +3, 1, 1. Always deduct 1 from the exponents of 2 and add 1 to all the +other exponents; then we get 1, 4, 2, 2, and half the product of these +four numbers will be the required number of ways in which 5,940 may be +the difference of two squares—that is, 8. To find these eight +squares, as it is an <i>even</i> number, we first divide by 4 and get 1485, +the eight pairs of factors of which are 1 × 1485, 3 × 495, 5 × 297, 9 +× 165, 11 × 135, 15 × 99, 27 × 55, and 33 × 45. The sum and difference +of any one of these pairs will give the required numbers. Thus, the +square of 1,486 less the square of 1,484 is 5,940, the square of 498 +less the square of 492 is the same, and so on. In the case of 63 +above, the number is <i>odd</i>; so we factorize at once, 1 × 63, 3 × 21, 7 +× 9. Then we find that <i>half</i> the sum and difference will give us the +numbers 32 and 31, 12 and 9, and 8 and 1, as shown in the solution to +the puzzle.</p> + +<p>The reverse problem, to find the factors of a number when you have +expressed it as the difference of two squares, is obvious. For +example, the sum and difference of any pair of numbers in the last +sentence will give us the factors of 63. Every prime number (except 1 +and 2) may be expressed as the difference of two squares in one way, +and in one way only. If a number can be expressed as the difference of +two squares in more than one way, it is composite; and having so +expressed it, we may at once obtain the factors, as we have seen. +Fermat showed in a letter to Mersenne or Frénicle, in 1643, how we may +discover whether a number may be expressed as the difference of two +squares in more than one way, or proved to be a prime. But the method, +when dealing with large numbers, is necessarily tedious, though in +practice it may be considerably shortened. In many cases it is the +shortest method known for factorizing large numbers, and I have always +held the opinion that Fermat used it in performing a certain feat in +factorizing that is historical and wrapped in mystery.</p> + +<hr style="width: 30%;" /> +<p><a name="X_140_FIND_ADAS_SURNAMEa" id="X_140_FIND_ADAS_SURNAMEa"></a><a href="#X_140_FIND_ADAS_SURNAME"><b>140.—FIND ADA'S SURNAME.—<i>solution</i></b></a></p> + +<p>The girls' names were Ada Smith, Annie Brown, Emily Jones, Mary +Robinson, and Bessie Evans.</p> + +<hr style="width: 30%;" /> +<p><a name="X_141_SATURDAY_MARKETINGa" id="X_141_SATURDAY_MARKETINGa"></a><a href="#X_141_SATURDAY_MARKETING"><b>141.—SATURDAY MARKETING.—<i>solution</i></b></a></p> + +<p>As every person's purchase was of the value of an exact number of +shillings, and as the party possessed when they started out forty +shilling coins altogether, there was no necessity for any lady to have +any smaller change, or any evidence that they actually had such +change. This being so, the only answer possible is that the women were +named respectively Anne Jones, Mary Robinson, Jane Smith, and Kate +Brown. It will now be found that there would be exactly eight +shillings left, which may be divided equally among the eight persons +in coin without any change being required.</p> + +<hr style="width: 30%;" /> +<p><a name="X_142_THE_SILK_PATCHWORKa" id="X_142_THE_SILK_PATCHWORKa"></a><a href="#X_142_THE_SILK_PATCHWORK"><b>142.—THE SILK PATCHWORK.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a142.png" width="400" height="397" alt="" title="" /> +</div> + +<p>Our illustration will show how to cut the stitches of the patchwork so +as to get the square F entire, and four equal pieces, G, H, I, K, that +will form a perfect Greek cross. The reader will know how to assemble +these four pieces from Fig. 13 in the article.</p> + + +<hr style="width: 30%;" /> +<p><a name="X_143_TWO_CROSSES_FROM_ONEa" id="X_143_TWO_CROSSES_FROM_ONEa"></a><a href="#X_143_TWO_CROSSES_FROM_ONE"><b>143.—TWO CROSSES FROM ONE.—<i>solution</i></b></a></p> + +<p>It will be seen that one cross is cut out entire, as A in Fig. 1, +while the four pieces marked <span class='pagenum'>Pg 169<a name="Page_169" id="Page_169"></a></span>B, C, D and E form the second cross, as +in Fig. 2, which will be of exactly the same size as the other. I will +leave the reader the pleasant task of discovering for himself the best +way of finding the direction of the cuts. Note that the Swastika again +appears.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a143.png" width="600" height="335" alt="" title="" /> +</div> + +<p>The difficult question now presents itself: How are we to cut three +Greek crosses from one in the fewest possible pieces? As a matter of +fact, this problem may be solved in as few as thirteen pieces; but as +I know many of my readers, advanced geometricians, will be glad to +have something to work on of which they are not shown the solution, I +leave the mystery for the present undisclosed.</p> + +<hr style="width: 30%;" /> +<p><a name="X_144_THE_CROSS_AND_THE_TRIANGLEa" id="X_144_THE_CROSS_AND_THE_TRIANGLEa"></a><a href="#X_144_THE_CROSS_AND_THE_TRIANGLE"><b>144.—THE CROSS AND THE TRIANGLE.—<i>solution</i></b></a></p> + +<p>The line A B in the following diagram represents the side of a square +having the same area as the cross. I have shown elsewhere, as stated, +how to make a square and equilateral triangle of equal area. I need +not go, therefore, into the preliminary question of finding the +dimensions of the triangle that is to equal our cross. We will assume +that we have already found this, and the question then becomes, How +are we to cut up one of these into pieces that will form the other?</p> + +<p>First draw the line A B where A and B are midway between the +extremities of the two side arms. Next make the lines D C and E F +equal in length to half the side of the triangle. Now from E and F +describe with the same radius the intersecting arcs at G and draw F G. +Finally make I K equal to H C and L B equal to A D. If we now draw I +L, it should be parallel to F G, and all the six pieces are marked +out. These fit together and form a perfect equilateral triangle, as +shown in the second diagram. Or we might have first found the +direction of the line M N in our triangle, then placed the point O +over the point E in the cross and turned round the triangle over the +cross until the line M N was parallel to A B. The piece 5 can then be +marked off and the other pieces in succession.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a144.png" width="600" height="331" alt="" title="" /> +</div> + +<p>I have seen many attempts at a solution involving the assumption that +the height of the triangle is exactly the same as the height of the +cross. This is a fallacy: the cross will always be higher than the +triangle of equal area.</p> + +<hr style="width: 30%;" /> +<p><a name="X_145_THE_FOLDED_CROSSa" id="X_145_THE_FOLDED_CROSSa"></a><a href="#X_145_THE_FOLDED_CROSS"><b>145.—THE FOLDED CROSS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a145a.png" width="400" height="264" alt="" title="" /> +</div> + +<p>First fold the cross along the dotted line A B in Fig. 1. You then +have it in the form shown in Fig. 2. Next fold it along the dotted +line C D (where D is, of course, the centre of the cross), and you get +the form shown in Fig. 3. Now take your scissors and cut from G to F, +and the four pieces, all of the same size and shape, will fit together +and form a square, as shown in Fig. 4.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a145b.png" width="400" height="251" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 170<a name="Page_170" id="Page_170"></a></span><a name="X_146_AN_EASY_DISSECTION_PUZZLEa" id="X_146_AN_EASY_DISSECTION_PUZZLEa"></a><a href="#X_146_AN_EASY_DISSECTION_PUZZLE"><b>146.—AN EASY DISSECTION PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a146.png" width="400" height="205" alt="" title="" /> +</div> + +<p>The solution to this puzzle is shown in the illustration. Divide the +figure up into twelve equal triangles, and it is easy to discover the +directions of the cuts, as indicated by the dark lines.</p> + +<hr style="width: 30%;" /> +<p><a name="X_147_AN_EASY_SQUARE_PUZZLEa" id="X_147_AN_EASY_SQUARE_PUZZLEa"></a><a href="#X_147_AN_EASY_SQUARE_PUZZLE"><b>147.—AN EASY SQUARE PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a147.png" width="400" height="386" alt="" title="" /> +</div> + +<p>The diagram explains itself, one of the five pieces having been cut in +two to form a square.</p> + +<hr style="width: 30%;" /> +<p><a name="X_148_THE_BUN_PUZZLEa" id="X_148_THE_BUN_PUZZLEa"></a><a href="#X_148_THE_BUN_PUZZLE"><b>148.—THE BUN PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a148.png" width="600" height="272" alt="" title="" /> +</div> + +<p>The secret of the bun puzzle lies in the fact that, with the relative +dimensions of the circles as given, the three diameters will form a +right-angled triangle, as shown by A, B, C. It follows that the two +smaller buns are exactly equal to the large bun. Therefore, if we give +David and Edgar the two halves marked D and E, they will have their +fair shares—one quarter of the confectionery each. Then if we place +the small bun, H, on the top of the remaining one and trace its +circumference in the manner shown, Fred's piece, F, will exactly equal +Harry's small bun, H, with the addition of the piece marked G—half +the rim of the other. Thus each boy gets an exactly equal share, and +there are only five pieces necessary.</p> + +<hr style="width: 30%;" /> +<p><a name="X_149_THE_CHOCOLATE_SQUARESa" id="X_149_THE_CHOCOLATE_SQUARESa"></a><a href="#X_149_THE_CHOCOLATE_SQUARES"><b>149.—THE CHOCOLATE SQUARES.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a149.png" width="400" height="400" alt="" title="" /> +</div> + +<p>Square A is left entire; the two pieces marked B fit together and make +a second square; the two pieces C make a third square; and the four +pieces marked D will form the fourth square.</p> + +<hr style="width: 30%;" /> +<p><a name="X_150_DISSECTING_A_MITREa" id="X_150_DISSECTING_A_MITREa"></a><a href="#X_150_DISSECTING_A_MITRE"><b>150.—DISSECTING A MITRE.—<i>solution</i></b></a></p> + +<p>The diagram on the next page shows how to cut into five pieces to form +a square. The dotted lines are intended to show how to find the points +C and F—the only difficulty. A B is half B D, and A E is parallel to +B H. With the point of the compasses at B describe the arc H E, and A +E will be the distance of C from B. Then F G equals B C less A B.</p> + +<p>This puzzle—with the added condition that it shall be cut into four +parts of the same size and shape—I have not been able to trace to an +earlier date than 1835. Strictly speaking, <span class='pagenum'>Pg 171<a name="Page_171" id="Page_171"></a></span>it is, in that form, +impossible of solution; but I give the answer that is always +presented, and that seems to satisfy most people.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a150a.png" width="600" height="282" alt="" title="" /> +</div> + +<p>We are asked to assume that the two portions containing the same +letter—AA, BB, CC, DD—are joined by "a mere hair," and are, +therefore, only one piece. To the geometrician this is absurd, and the +four shares are not equal in area unless they consist of two pieces +each. If you make them equal in area, they will not be exactly alike +in shape.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a150b.png" width="400" height="388" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_151_THE_JOINERS_PROBLEMa" id="X_151_THE_JOINERS_PROBLEMa"></a><a href="#X_151_THE_JOINERS_PROBLEM"><b>151.—THE JOINER'S PROBLEM.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a151.png" width="400" height="254" alt="" title="" /> +</div> + +<p>Nothing could be easier than the solution of this puzzle—when you +know how to do it. And yet it is apt to perplex the novice a good deal +if he wants to do it in the fewest possible pieces—three. All you +have to do is to find the point A, midway between B and C, and then +cut from A to D and from A to E. The three pieces then form a square +in the manner shown. Of course, the proportions of the original figure +must be correct; thus the triangle BEF is just a quarter of the square +BCDF. Draw lines from B to D and from C to F and this will be clear.</p> + +<hr style="width: 30%;" /> +<p><a name="X_152_ANOTHER_JOINERS_PROBLEMa" id="X_152_ANOTHER_JOINERS_PROBLEMa"></a><a href="#X_152_ANOTHER_JOINERS_PROBLEM"><b>152.—ANOTHER JOINER'S PROBLEM.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a152.png" width="400" height="389" alt="" title="" /> +</div> + +<p>The point was to find a general rule for forming a perfect square out +of another square combined with a "right-angled isosceles triangle." +The triangle to which geometricians give this high-sounding name is, +of course, nothing more or less than half a square that has been +divided from corner to corner.</p> + +<p>The precise relative proportions of the square and triangle are of no +consequence whatever. <span class='pagenum'>Pg 172<a name="Page_172" id="Page_172"></a></span>It is only necessary to cut the wood or +material into five pieces.</p> + +<p>Suppose our original square to be ACLF in the above diagram and our +triangle to be the shaded portion CED. Now, we first find half the +length of the long side of the triangle (CD) and measure off this +length at AB. Then we place the triangle in its present position +against the square and make two cuts—one from B to F, and the other +from B to E. Strange as it may seem, that is all that is necessary! If +we now remove the pieces G, H, and M to their new places, as shown in +the diagram, we get the perfect square BEKF.</p> + +<p>Take any two square pieces of paper, of different sizes but perfect +squares, and cut the smaller one in half from corner to corner. Now +proceed in the manner shown, and you will find that the two pieces may +be combined to form a larger square by making these two simple cuts, +and that no piece will be required to be turned over.</p> + +<p>The remark that the triangle might be "a little larger or a good deal +smaller in proportion" was intended to bar cases where area of +triangle is greater than area of square. In such cases six pieces are +necessary, and if triangle and square are of equal area there is an +obvious solution in three pieces, by simply cutting the square in half +diagonally.</p> + +<hr style="width: 30%;" /> +<p><a name="X_153_A_CUTTING-OUT_PUZZLEa" id="X_153_A_CUTTING-OUT_PUZZLEa"></a><a href="#X_153_A_CUTTING-OUT_PUZZLE"><b>153.—A CUTTING-OUT PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a153.png" width="400" height="300" alt="" title="" /> +</div> + +<p>The illustration shows how to cut the four pieces and form with them a +square. First find the side of the square (the mean proportional +between the length and height of the rectangle), and the method is +obvious. If our strip is exactly in the proportions 9x1, or 16x1, or +25x1, we can clearly cut it in 3, 4, or 5 rectangular pieces +respectively to form a square. Excluding these special cases, the +general law is that for a strip in length more than n² times the +breadth, and not more than (n+1)² times the breadth, it may be cut in +n+2 pieces to form a square, and there will be n-1 rectangular pieces +like piece 4 in the diagram. Thus, for example, with a strip 24x1, the +length is more than 16 and less than 25 times the breadth. Therefore +it can be done in 6 pieces (n here being 4), 3 of which will be +rectangular. In the case where n equals 1, the rectangle disappears +and we get a solution in three pieces. Within these limits, of course, +the sides need not be rational: the solution is purely geometrical.</p> + +<hr style="width: 30%;" /> +<p><a name="X_154_MRS_HOBSONS_HEARTHRUGa" id="X_154_MRS_HOBSONS_HEARTHRUGa"></a><a href="#X_154_MRS_HOBSONS_HEARTHRUG"><b>154.—MRS. HOBSON'S HEARTHRUG.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a154.png" width="400" height="297" alt="" title="" /> +</div> + +<p>As I gave full measurements of the mutilated rug, it was quite an easy +matter to find the precise dimensions for the square. The two pieces +cut off would, if placed together, make an oblong piece 12x6, giving +an area of 72 (inches or yards, as we please), and as the original +complete rug measured 36x27, it had an area of 972. If, therefore, we +deduct the pieces that have been cut away, we find that our new rug +will contain 972 less 72, or 900; and as 900 is the square of 30, we +know that the new rug must measure 30x30 to be a perfect square. This +is a great help towards the solution, because we may safely conclude +that the two horizontal sides measuring 30 each may be left intact.</p> + +<p>There is a very easy way of solving the puzzle in four pieces, and +also a way in three pieces that can scarcely be called difficult, but +the correct answer is in only two pieces.</p> + +<p>It will be seen that if, after the cuts are made, we insert the teeth +of the piece B one tooth lower down, the two portions will fit +together and form a square.</p> + +<hr style="width: 30%;" /> +<p><a name="X_155_THE_PENTAGON_AND_SQUAREa" id="X_155_THE_PENTAGON_AND_SQUAREa"></a><a href="#X_155_THE_PENTAGON_AND_SQUARE"><b>155.—THE PENTAGON AND SQUARE.—<i>solution</i></b></a></p> + +<p>A regular pentagon may be cut into as few as six pieces that will fit +together without any turning over and form a square, as I shall show +below. Hitherto the best answer has been in seven pieces—the solution +produced some years ago by a foreign mathematician, Paul Busschop. We +first form a parallelogram, and from that the square. The process will +be seen in the diagram on the next page.</p> + +<p>The pentagon is ABCDE. By the cut AC and the cut FM (F being the +middle point between A and C, and M being the same distance from A as +F) we get two pieces that may be placed in position at GHEA and form +the parallelogram GHDC. We then find the mean proportional between the +length HD and the <i>height</i> of the parallelogram. This distance we mark +off from C at K, then draw CK, <span class='pagenum'>Pg 173<a name="Page_173" id="Page_173"></a></span>and from G drop the line GL, +perpendicular to KC. The rest is easy and rather obvious. It will be +seen that the six pieces will form either the pentagon or the square.</p> + +<p>I have received what purported to be a solution in five pieces, but +the method was based on the rather subtle fallacy that half the +diagonal plus half the side of a pentagon equals the side of a square +of the same area. I say subtle, because it is an extremely close +approximation that will deceive the eye, and is quite difficult to +prove inexact. I am not aware that attention has before been drawn to +this curious approximation.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a155.png" width="400" height="367" alt="" title="" /> +</div> + +<p>Another correspondent made the side of his square 1¼ of the side of +the pentagon. As a matter of fact, the ratio is irrational. I +calculate that if the side of the pentagon is 1—inch, foot, or +anything else—the side of the square of equal area is 1.3117 nearly, +or say roughly 1<sup>3</sup>/<sub>10</sub>. So we can only hope to solve the puzzle by +geometrical methods.</p> + +<hr style="width: 30%;" /> +<p><a name="X_156_THE_DISSECTED_TRIANGLEa" id="X_156_THE_DISSECTED_TRIANGLEa"></a><a href="#X_156_THE_DISSECTED_TRIANGLE"><b>156.—THE DISSECTED TRIANGLE.—<i>solution</i></b></a></p> + +<p>Diagram A is our original triangle. We will say it measures 5 inches +(or 5 feet) on each side. If we take off a slice at the bottom of any +equilateral triangle by a cut parallel with the base, the portion that +remains will always be an equilateral triangle; so we first cut off +piece 1 and get a triangle 3 inches on every side. The manner of +finding directions of the other cuts in A is obvious from the diagram.</p> + +<p>Now, if we want two triangles, 1 will be one of them, and 2, 3, 4, and +5 will fit together, as in B, to form the other. If we want three +equilateral triangles, 1 will be one, 4 and 5 will form the second, as +in C, and 2 and 3 will form the third, as in D. In B and C the piece 5 +is turned over; but there can be no objection to this, as it is not +forbidden, and is in no way opposed to the nature of the puzzle.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a156.png" width="400" height="492" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_157_THE_TABLE-TOP_AND_STOOLSa" id="X_157_THE_TABLE-TOP_AND_STOOLSa"></a><a href="#X_157_THE_TABLE-TOP_AND_STOOLS"><b>157.—THE TABLE-TOP AND STOOLS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a157a.png" width="400" height="400" alt="" title="" /> +</div> + +<p>One object that I had in view when presenting this little puzzle was +to point out the uncertainty of the meaning conveyed by the word +"oval." Though originally derived from the Latin word <i>ovum</i>, an egg, +yet what we understand as the egg-shape (with one end smaller than the +other) is only one of many forms of the oval; while some eggs are +spherical in shape, and a sphere or circle is most certainly not an +oval. If we speak of an ellipse—a conical ellipse—we are on safer +ground, but here we must be careful of error. I recollect a Liverpool +town councillor, many years ago, whose ignorance of the poultry-yard +led him to substitute the word "hen" for "fowl," remarking, "We must +remember, gentlemen, that although every cock is a hen, every hen is +not a cock!" Similarly, we must always note that although every +ellipse is an oval, every oval is not an <span class='pagenum'>Pg 174<a name="Page_174" id="Page_174"></a></span>ellipse. It is correct to +say that an oval is an oblong curvilinear figure, having two unequal +diameters, and bounded by a curve line returning into itself; and this +includes the ellipse, but all other figures which in any way approach +towards the form of an oval without necessarily having the properties +above described are included in the term "oval." Thus the following +solution that I give to our puzzle involves the pointed "oval," known +among architects as the "vesica piscis."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a157b.png" width="400" height="298" alt="" title="" /> +</div> + +<p>The dotted lines in the table are given for greater clearness, the +cuts being made along the other lines. It will be seen that the eight +pieces form two stools of exactly the same size and shape with similar +hand-holes. These holes are a trifle longer than those in the +schoolmaster's stools, but they are much narrower and of considerably +smaller area. Of course 5 and 6 can be cut out in one piece—also 7 +and 8—making only <i>six pieces</i> in all. But I wished to keep the same +number as in the original story.</p> + +<p>When I first gave the above puzzle in a London newspaper, in +competition, no correct solution was received, but an ingenious and +neatly executed attempt by a man lying in a London infirmary was +accompanied by the following note: "Having no compasses here, I was +compelled to improvise a pair with the aid of a small penknife, a bit +of firewood from a bundle, a piece of tin from a toy engine, a tin +tack, and two portions of a hairpin, for points. They are a fairly +serviceable pair of compasses, and I shall keep them as a memento of +your puzzle."</p> + +<hr style="width: 30%;" /> +<p><a name="X_158_THE_GREAT_MONADa" id="X_158_THE_GREAT_MONADa"></a><a href="#X_158_THE_GREAT_MONAD"><b>158.—THE GREAT MONAD.—<i>solution</i></b></a></p> + +<p>The areas of circles are to each other as the squares of their +diameters. If you have a circle 2 in. in diameter and another 4 in. in +diameter, then one circle will be four times as great in area as the +other, because the square of 4 is four times as great as the square of +2. Now, if we refer to Diagram 1, we see how two equal squares may be +cut into four pieces that will form one larger square; from which it +is self-evident that any square has just half the area of the square +of its diagonal. In Diagram 2 I have introduced a square as it often +occurs in ancient drawings of the Monad; which was my reason for +believing that the symbol had mathematical meanings, since it will be +found to demonstrate the fact that the area of the outer ring or +annulus is exactly equal to the area of the inner circle. Compare +Diagram 2 with Diagram 1, and you will see that as the square of the +diameter CD is double the square of the diameter of the inner circle, +or CE, therefore the area of the larger circle is double the area of +the smaller one, and consequently the area of the annulus is exactly +equal to that of the inner circle. This answers our first question.</p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/a158.png" width="500" height="485" alt="" title="" /> +</div> + +<p>In Diagram 3 I show the simple solution to the second question. It is +obviously correct, and may be proved by the cutting and superposition +of parts. The dotted lines will also serve to make it evident. The +third question is solved by the cut CD in Diagram 2, but it remains to +be proved that the piece F is really one-half of the Yin or the Yan. +This we will <span class='pagenum'>Pg 175<a name="Page_175" id="Page_175"></a></span>do in Diagram 4. The circle K has one-quarter the area +of the circle containing Yin and Yan, because its diameter is just +one-half the length. Also L in Diagram 3 is, we know, one-quarter the +area. It is therefore evident that G is exactly equal to H, and +therefore half G is equal to half H. So that what F loses from L it +gains from K, and F must be half of Yin or Yan.</p> + +<hr style="width: 30%;" /> +<p><a name="X_159_THE_SQUARE_OF_VENEERa" id="X_159_THE_SQUARE_OF_VENEERa"></a><a href="#X_159_THE_SQUARE_OF_VENEER"><b>159.—THE SQUARE OF VENEER.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a159.png" width="400" height="394" alt="" title="" /> +</div> + +<p>Any square number may be expressed as the sum of two squares in an +infinite number of different ways. The solution of the present puzzle +forms a simple demonstration of this rule. It is a condition that we +give actual dimensions.</p> + +<p>In this puzzle I ignore the known dimensions of our square and work on +the assumption that it is 13n by 13n. The value of n we can afterwards +determine. Divide the square as shown (where the dotted lines indicate +the original markings) into 169 squares. As 169 is the sum of the two +squares 144 and 25, we will proceed to divide the veneer into two +squares, measuring respectively 12x12 and 5x5; and as we know that two +squares may be formed from one square by dissection in four pieces, we +seek a solution in this number. The dark lines in the diagram show +where the cuts are to be made. The square 5x5 is cut out whole, and +the larger square is formed from the remaining three pieces, B, C, and +D, which the reader can easily fit together.</p> + +<p>Now, n is clearly <sup>5</sup>/<sub>13</sub> of an inch. Consequently our larger square must +be <sup>60</sup>/<sub>13</sub> in. × <sup>60</sup>/<sub>13</sub> in., and our smaller square <sup>25</sup>/<sub>13</sub> in. × <sup>25</sup>/<sub>13</sub> in. +The square of <sup>60</sup>/<sub>13</sub> added to the square of <sup>25</sup>/<sub>13</sub> is 25. The square is +thus divided into as few as four pieces that form two squares of known +dimensions, and all the sixteen nails are avoided.</p> + +<p>Here is a general formula for finding two squares whose sum shall +equal a given square, say a². In the case of the solution of our +puzzle p = 3, q = 2, and a = 5.</p> + +<div style="font-size: larger;"> +<pre> + _________________________ + 2pqa \/ a²( p² + q²)² - (2pqa)² + --------- = x; --------------------------- = y + p² + q² p² + q² + + Here x² + y² = a². +</pre> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_160_THE_TWO_HORSESHOESa" id="X_160_THE_TWO_HORSESHOESa"></a><a href="#X_160_THE_TWO_HORSESHOES"><b>160.—THE TWO HORSESHOES.—<i>solution</i></b></a></p> + +<p>The puzzle was to cut the two shoes (including the hoof contained +within the outlines) into four pieces, two pieces each, that would fit +together and form a perfect circle. It was also stipulated that all +four pieces should be different in shape. As a matter of fact, it is a +puzzle based on the principle contained in that curious Chinese symbol +the Monad. (See No. <a href="#X_158_THE_GREAT_MONAD">158</a>.)</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a160.png" width="600" height="262" alt="" title="" /> +</div> + +<p>The above diagrams give the correct solution to the problem. It will +be noticed that 1 and 2 are cut into the required four pieces, all +differ<span class='pagenum'>Pg 176<a name="Page_176" id="Page_176"></a></span>ent in shape, that fit together and form the perfect circle +shown in Diagram 3. It will further be observed that the two pieces A +and B of one shoe and the two pieces C and D of the other form two +exactly similar halves of the circle—the Yin and the Yan of the great +Monad. It will be seen that the shape of the horseshoe is more easily +determined from the circle than the dimensions of the circle from the +horseshoe, though the latter presents no difficulty when you know that +the curve of the long side of the shoe is part of the circumference of +your circle. The difference between B and D is instructive, and the +idea is useful in all such cases where it is a condition that the +pieces must be different in shape. In forming D we simply add on a +symmetrical piece, a curvilinear square, to the piece B. Therefore, in +giving either B or D a quarter turn before placing in the new +position, a precisely similar effect must be produced.</p> + +<hr style="width: 30%;" /> +<p><a name="X_161_THE_BETSY_ROSS_PUZZLEa" id="X_161_THE_BETSY_ROSS_PUZZLEa"></a><a href="#X_161_THE_BETSY_ROSS_PUZZLE"><b>161.—THE BETSY ROSS PUZZLE.—<i>solution</i></b></a></p> + +<p>Fold the circular piece of paper in half along the dotted line shown +in Fig. 1, and divide the upper half into five equal parts as +indicated. Now fold the paper along the lines, and it will have the +appearance shown in Fig. 2. If you want a star like Fig. 3, cut from A +to B; if you wish one like Fig. 4, cut from A to C. Thus, the nearer +you cut to the point at the bottom the longer will be the points of +the star, and the farther off from the point that you cut the shorter +will be the points of the star.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a161.png" width="600" height="447" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_162_THE_CARDBOARD_CHAINa" id="X_162_THE_CARDBOARD_CHAINa"></a><a href="#X_162_THE_CARDBOARD_CHAIN"><b>162.—THE CARDBOARD CHAIN.—<i>solution</i></b></a></p> + +<p>The reader will probably feel rewarded for any care and patience that +he may bestow on cutting out the cardboard chain. We will suppose that +he has a piece of cardboard measuring 8 in. by 2½ in., though the +dimensions are of no importance. Yet if you want a long chain you must, +of course, take a long strip of cardboard. First rule pencil lines B B +and C C, half an inch from the edges, and also the short perpendicular +lines half an inch apart. Rule lines on the other side in just the same +way, and in order that they shall coincide it is well to prick through +the card with a needle the points where the short lines end. Now take +your penknife and split the card from A A down to B B, and from D D up +to C C. Then cut right through the card along all the short +perpendicular lines, and half through the card along the short portions +of B B and C C that are not dotted. Next turn the card over and cut half +through along the short lines on B B and C C at the places that are +immediately beneath the dotted lines on the upper side. With a little +careful separation of the parts with the penknife, the cardboard may now +be divided into two interlacing ladder-like portions, as shown in Fig. +2; and if you cut away all the shaded parts you will get the chain, cut +solidly out of the cardboard, without any join, as shown in the +illustrations on page 40.</p> + +<p>It is an interesting variant of the puzzle to cut out two keys on a +ring—in the same manner without join.</p> + +<p><span class='pagenum'>Pg 177<a name="Page_177" id="Page_177"></a></span></p><div class="figcenter" style="width: 600px;"> +<img src="images/a162.png" width="600" height="422" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_164_THE_POTATO_PUZZLEa" id="X_164_THE_POTATO_PUZZLEa"></a><a href="#X_164_THE_POTATO_PUZZLE"><b>164.—THE POTATO PUZZLE.—<i>solution</i></b></a></p> + +<p>As many as twenty-two pieces may be obtained by the six cuts. The +illustration shows a pretty symmetrical solution. The rule in such +cases is that every cut shall intersect every other cut and no two +intersections coincide; that is to say, every line passes through +every other line, but more than two lines do not cross at the same +point anywhere. There are other ways of making the cuts, but this rule +must always be observed if we are to get the full number of pieces.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a164.png" width="400" height="394" alt="" title="" /> +</div> + +<p>The general formula is that with <i>n</i> cuts we can always produce <sup>(<i>n</i>(<i>n</i> + 1) + 1)</sup>/<sub>2</sub> . One of the problems proposed by the late Sam Loyd +was to produce the maximum number of pieces by <i>n</i> straight cuts +through a solid cheese. Of course, again, the pieces cut off may not +be moved or piled. Here we have to deal with the intersection of +planes (instead of lines), and the general formula is that with <i>n</i> +cuts we may produce <sup>((<i>n</i> - 1)<i>n</i>(<i>n</i> + 1))</sup>/<sub>6</sub> + <i>n</i> + 1 pieces. +It is extremely difficult to "see" the direction and effects of the +successive cuts for more than a few of the lowest values of <i>n</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_165_THE_SEVEN_PIGSa" id="X_165_THE_SEVEN_PIGSa"></a><a href="#X_165_THE_SEVEN_PIGS"><b>165.—THE SEVEN PIGS.—<i>solution</i></b></a></p> + +<p>The illustration shows the direction for placing the three fences so +as to enclose every pig in a separate sty. The greatest number of +spaces that can be enclosed with three straight lines in a square is +seven, as shown in the last puzzle. Bearing this fact in mind, the +puzzle must be solved by trial.</p> + +<p><span class='pagenum'>Pg 178<a name="Page_178" id="Page_178"></a></span></p><div class="figcenter" style="width: 400px;"> +<img src="images/a165.png" width="400" height="394" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_166_THE_LANDOWNERS_FENCESa" id="X_166_THE_LANDOWNERS_FENCESa"></a><a href="#X_166_THE_LANDOWNERS_FENCES"><b>166.—THE LANDOWNER'S FENCES.—<i>solution</i></b></a></p> + +<p>Four fences only are necessary, as follows:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a166.png" width="400" height="392" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_167_THE_WIZARDS_CATSa" id="X_167_THE_WIZARDS_CATSa"></a><a href="#X_167_THE_WIZARDS_CATS"><b>167.—THE WIZARD'S CATS.—<i>solution</i></b></a></p> + +<p>The illustration requires no explanation. It shows clearly how the +three circles may be drawn so that every cat has a separate enclosure, +and cannot approach another cat without crossing a line.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a167.png" width="400" height="400" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_168_THE_CHRISTMAS_PUDDINGa" id="X_168_THE_CHRISTMAS_PUDDINGa"></a><a href="#X_168_THE_CHRISTMAS_PUDDING"><b>168.—THE CHRISTMAS PUDDING.—<i>solution</i></b></a></p> + +<p>The illustration shows how the pudding may be cut into two parts of +exactly the same size and shape. The lines must necessarily pass +through the points A, B, C, D, and E. But, subject to this condition, +they may be varied in an infinite number of ways. For example, at a +point midway between A and the edge, the line may be completed in an +unlimited number of ways (straight or crooked), provided it be exactly +reflected from E to the opposite edge. And similar variations may be +introduced at other places.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a168.png" width="400" height="400" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_169_A_TANGRAM_PARADOXa" id="X_169_A_TANGRAM_PARADOXa"></a><a href="#X_169_A_TANGRAM_PARADOX"><b>169.—A TANGRAM PARADOX.—<i>solution</i></b></a></p> + +<p>The diagrams will show how the figures are constructed—each with the +seven Tangrams. It will be noticed that in both cases the head, hat, +and arm are precisely alike, and the width at the base of the body the +same. But this body contains four pieces in the first case, and in the +second design only three. The first is larger than the second by +exactly that narrow strip indicated by the dotted line between A and +B. <span class='pagenum'>Pg 179<a name="Page_179" id="Page_179"></a></span>This strip is therefore exactly equal in area to the piece forming +the foot in the other design, though when thus distributed along the +side of the body the increased dimension is not easily apparent to the +eye.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a169.png" width="400" height="368" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_170_THE_CUSHION_COVERSa" id="X_170_THE_CUSHION_COVERSa"></a><a href="#X_170_THE_CUSHION_COVERS"><b>170.—THE CUSHION COVERS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a170.png" width="400" height="419" alt="" title="" /> +</div> + +<p>The two pieces of brocade marked A will fit together and form one +perfect square cushion top, and the two pieces marked B will form the +other.</p> + +<hr style="width: 30%;" /> +<p><a name="X_171_THE_BANNER_PUZZLEa" id="X_171_THE_BANNER_PUZZLEa"></a><a href="#X_171_THE_BANNER_PUZZLE"><b>171.—THE BANNER PUZZLE.—<i>solution</i></b></a></p> + +<p>The illustration explains itself. Divide the bunting into 25 squares +(because this number is the sum of two other squares—16 and 9), and +then cut along the thick lines. The two pieces marked A form one +square, and the two pieces marked B form the other.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a171.png" width="400" height="400" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_172_MRS_SMILEYS_CHRISTMAS_PRESENTa" id="X_172_MRS_SMILEYS_CHRISTMAS_PRESENTa"></a><a href="#X_172_MRS_SMILEYS_CHRISTMAS_PRESENT"><b>172.—MRS. SMILEY'S CHRISTMAS PRESENT.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a172.png" width="400" height="794" alt="" title="" /> +</div> + +<p><span class='pagenum'>Pg 180<a name="Page_180" id="Page_180"></a></span>The first step is to find six different square numbers that sum to +196. For example, 1 + 4 + 25 + 36 + 49 + 81 = 196; 1 + 4 + 9 + 25 + 36 ++ 121 = 196; 1 + 9 + 16 + 25 + 64 + 81 = 196. The rest calls for +individual judgment and ingenuity, and no definite rules can be given +for procedure. The annexed diagrams will show solutions for the first +two cases stated. Of course the three pieces marked A and those marked +B will fit together and form a square in each case. The assembling of +the parts may be slightly varied, and the reader may be interested in +finding a solution for the third set of squares I have given.</p> + +<hr style="width: 30%;" /> +<p><a name="X_173_MRS_PERKINSS_QUILTa" id="X_173_MRS_PERKINSS_QUILTa"></a><a href="#X_173_MRS_PERKINSS_QUILT"><b>173.—MRS. PERKINS'S QUILT.—<i>solution</i></b></a></p> + +<p>The following diagram shows how the quilt should be constructed.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a173.png" width="400" height="392" alt="" title="" /> +</div> + +<p>There is, I believe, practically only one solution to this puzzle. The +fewest separate squares must be eleven. The portions must be of the +sizes given, the three largest pieces must be arranged as shown, and +the remaining group of eight squares may be "reflected," but cannot be +differently arranged.</p> + +<hr style="width: 30%;" /> +<p><a name="X_174_THE_SQUARES_OF_BROCADEa" id="X_174_THE_SQUARES_OF_BROCADEa"></a><a href="#X_174_THE_SQUARES_OF_BROCADE"><b>174.—THE SQUARES OF BROCADE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a174a.png" width="400" height="415" alt="" title="" /> +</div> + +<p>So far as I have been able to discover, there is only one possible +solution to fulfil the conditions. The pieces fit together as in +Diagram 1, Diagrams 2 and 3 showing how the two original squares are +to be cut. It will be seen that the pieces A and C have each twenty +chequers, and are therefore of equal area. Diagram 4 (built up with +the dissected square No. 5) solves the puzzle, except for the small +condition contained in the words, "I cut the <i>two</i> squares in the +manner desired." In this case the smaller square is preserved intact. +Still I give it as an illustration of a feature of the puzzle. It is +impossible in a problem of this kind to give a <i>quarter-turn</i> to any +of the pieces if the pattern is to properly match, but (as in the case +of F, in Diagram 4) we may give a symmetrical piece a +<i>half-turn</i>—that is, turn it upside down. Whether or not a piece may +be given a quarter-turn, a half-turn, or no turn at all in these +chequered problems, depends on the character of the design, on the +material employed, and also on the form of the piece itself.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a174b.png" width="400" height="225" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a174c.png" width="400" height="431" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a174d.png" width="400" height="442" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_175_ANOTHER_PATCHWORK_PUZZLEa" id="X_175_ANOTHER_PATCHWORK_PUZZLEa"></a><a href="#X_175_ANOTHER_PATCHWORK_PUZZLE"><b>175.—ANOTHER PATCHWORK PUZZLE.—<i>solution</i></b></a></p> + +<p>The lady need only unpick the stitches along the dark lines in the +larger portion of patchwork, <span class='pagenum'>Pg 181<a name="Page_181" id="Page_181"></a></span>when the four pieces will fit together +and form a square, as shown in our illustration.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a175.png" width="400" height="173" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_176_LINOLEUM_CUTTINGa" id="X_176_LINOLEUM_CUTTINGa"></a><a href="#X_176_LINOLEUM_CUTTING"><b>176.—LINOLEUM CUTTING.—<i>solution</i></b></a></p> + +<p>There is only one solution that will enable us to retain the larger of +the two pieces with as little as possible cut from it. Fig. 1 in the +following diagram shows how the smaller piece is to be cut, and Fig. 2 +how we should dissect the larger piece, while in Fig. 3 we have the +new square 10 × 10 formed by the four pieces with all the chequers +properly matched. It will be seen that the piece D contains fifty-two +chequers, and this is the largest piece that it is possible to +preserve under the conditions.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a176.png" width="400" height="543" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_177_ANOTHER_LINOLEUM_PUZZLEa" id="X_177_ANOTHER_LINOLEUM_PUZZLEa"></a><a href="#X_177_ANOTHER_LINOLEUM_PUZZLE"><b>177.—ANOTHER LINOLEUM PUZZLE.—<i>solution</i></b></a></p> + +<p>Cut along the thick lines, and the four pieces will fit together and +form a perfect square in the manner shown in the smaller diagram.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a177.png" width="400" height="236" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_178_THE_CARDBOARD_BOXa" id="X_178_THE_CARDBOARD_BOXa"></a><a href="#X_178_THE_CARDBOARD_BOX"><b>178.—THE CARDBOARD BOX.—<i>solution</i></b></a></p> + +<p>The areas of the top and side multiplied together and divided by the +area of the end give the square of the length. Similarly, the product +of top and end divided by side gives the square of the breadth; and +the product of side and end divided by the top gives the square of the +depth. But we only need one of these operations. Let us take the +first. Thus, 120 × 96 divided by 80 equals 144, the square of 12. +Therefore the length is 12 inches, from which we can, of course, at +once get the breadth and depth—10 in. and 8 in. respectively.</p> + +<hr style="width: 30%;" /> +<p><a name="X_179_STEALING_THE_BELL-ROPESa" id="X_179_STEALING_THE_BELL-ROPESa"></a><a href="#X_179_STEALING_THE_BELL-ROPES"><b>179.—STEALING THE BELL-ROPES.—<i>solution</i></b></a></p> + +<p>Whenever we have one side (<i>a</i>) of a right-angled triangle, and know the +difference between the second side and the hypotenuse (which +difference we will call <i>b</i>), then the length of the hypotenuse will be</p> + +<p class='center'><span class='su2'><i>a</i><sup>2</sup></span>/<sub>2<i>b</i></sub> + <sup><i>b</i></sup>/<sub>2</sub></p> + +<p>In the case of our puzzle this will be</p> + +<p class='center'><sup>(48 × 48)</sup>/<sub>6</sub> + 1½ in. = 32 ft. 1½ in.,</p> + +<p>which is the length of the rope.</p> + +<hr style="width: 30%;" /> +<p><a name="X_180_THE_FOUR_SONSa" id="X_180_THE_FOUR_SONSa"></a><a href="#X_180_THE_FOUR_SONS"><b>180.—THE FOUR SONS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a180.png" width="400" height="400" alt="" title="" /> +</div> + +<p>The diagram shows the most equitable division of the land possible, +"so that each son shall receive land of exactly the same area and +exactly similar in shape," and so that each shall have access to the +well in the centre without trespass on another's land. The conditions +<span class='pagenum'>Pg 182<a name="Page_182" id="Page_182"></a></span>do not require that each son's land shall be in one piece, but it is +necessary that the two portions assigned to an individual should be +kept apart, or two adjoining portions might be held to be one piece, +in which case the condition as to shape would have to be broken. At +present there is only one shape for each piece of land—half a square +divided diagonally. And A, B, C, and D can each reach their land from +the outside, and have each equal access to the well in the centre.</p> + +<hr style="width: 30%;" /> +<p><a name="X_181_THE_THREE_RAILWAY_STATIONSa" id="X_181_THE_THREE_RAILWAY_STATIONSa"></a><a href="#X_181_THE_THREE_RAILWAY_STATIONS"><b>181.—THE THREE RAILWAY STATIONS.—<i>solution</i></b></a></p> + +<p>The three stations form a triangle, with sides 13, 14, and 15 miles. +Make the 14 side the base; then the height of the triangle is 12 and +the area 84. Multiply the three sides together and divide by four +times the area. The result is eight miles and one-eighth, the distance +required.</p> + +<hr style="width: 30%;" /> +<p><a name="X_182_THE_GARDEN_PUZZLEa" id="X_182_THE_GARDEN_PUZZLEa"></a><a href="#X_182_THE_GARDEN_PUZZLE"><b>182.—THE GARDEN PUZZLE.—<i>solution</i></b></a></p> + +<p>Half the sum of the four sides is 144. From this deduct in turn the +four sides, and we get 64, 99, 44, and 81. Multiply these together, +and we have as the result the square of 4,752. Therefore the garden +contained 4,752 square yards. Of course the tree being equidistant +from the four corners shows that the garden is a quadrilateral that +may be inscribed in a circle.</p> + +<hr style="width: 30%;" /> +<p><a name="X_183_DRAWING_A_SPIRALa" id="X_183_DRAWING_A_SPIRALa"></a><a href="#X_183_DRAWING_A_SPIRAL"><b>183.—DRAWING A SPIRAL.—<i>solution</i></b></a></p> + +<p>Make a fold in the paper, as shown by the dotted line in the +illustration. Then, taking any two points, as A and B, describe +semicircles on the line alternately from the centres B and A, being +careful to make the ends join, and the thing is done. Of course this +is not a <i>true</i> spiral, but the puzzle was to produce the <i>particular</i> +spiral that was shown, and that was drawn in this simple manner.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a183.png" width="600" height="600" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_184_HOW_TO_DRAW_AN_OVALa" id="X_184_HOW_TO_DRAW_AN_OVALa"></a><a href="#X_184_HOW_TO_DRAW_AN_OVAL"><b>184.—HOW TO DRAW AN OVAL.—<i>solution</i></b></a></p> + +<p>If you place your sheet of paper round the surface of a cylindrical +bottle or canister, the oval can be drawn with one sweep of the +compasses.</p> + +<hr style="width: 30%;" /> +<p><a name="X_185_ST_GEORGES_BANNERa" id="X_185_ST_GEORGES_BANNERa"></a><a href="#X_185_ST_GEORGES_BANNER"><b>185.—ST. GEORGE'S BANNER.—<i>solution</i></b></a></p> + +<p>As the flag measures 4 ft. by 3 ft., the length of the diagonal (from +corner to corner) is 5 ft. All you need do is to deduct half the +length of this diagonal (2½ ft.) from a quarter of the distance all +round the edge of the flag (3½ ft.)—a quarter of 14 ft. The +difference (1 ft.) is the required width of the arm of the red cross. +The area of the cross will then be the same as that of the white +ground.</p> + +<hr style="width: 30%;" /> +<p><a name="X_186_THE_CLOTHES_LINE_PUZZLEa" id="X_186_THE_CLOTHES_LINE_PUZZLEa"></a><a href="#X_186_THE_CLOTHES_LINE_PUZZLE"><b>186.—THE CLOTHES LINE PUZZLE.—<i>solution</i></b></a></p> + +<p>Multiply together, and also add together, the heights of the two poles +and divide one result <span class='pagenum'>Pg 183<a name="Page_183" id="Page_183"></a></span>by the other. That is, if the two heights are <i>a</i> +and <i>b</i> respectively, then <sup><i>ab</i></sup>/<sub>(<i>a</i> + <i>b</i>)</sub> will give the height of the +intersection. In the particular case of our puzzle, the intersection +was therefore 2 ft. 11 in. from the ground. The distance that the +poles are apart does not affect the answer. The reader who may have +imagined that this was an accidental omission will perhaps be +interested in discovering the reason why the distance between the +poles may be ignored.</p> + +<hr style="width: 30%;" /> +<p><a name="X_187_THE_MILKMAID_PUZZLEa" id="X_187_THE_MILKMAID_PUZZLEa"></a><a href="#X_187_THE_MILKMAID_PUZZLE"><b>187.—THE MILKMAID PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a187.png" width="400" height="442" alt="" title="" /> +</div> + +<p>Draw a straight line, as shown in the diagram, from the milking-stool +perpendicular to the near bank of the river, and continue it to the +point A, which is the same distance from that bank as the stool. If +you now draw the straight line from A to the door of the dairy, it +will cut the river at B. Then the shortest route will be from the +stool to B and thence to the door. Obviously the shortest distance +from A to the door is the straight line, and as the distance from the +stool to any point of the river is the same as from A to that point, +the correctness of the solution will probably appeal to every reader +without any acquaintance with geometry.</p> + +<hr style="width: 30%;" /> +<p><a name="X_188_THE_BALL_PROBLEMa" id="X_188_THE_BALL_PROBLEMa"></a><a href="#X_188_THE_BALL_PROBLEM"><b>188.—THE BALL PROBLEM.—<i>solution</i></b></a></p> + +<p>If a round ball is placed on the level ground, six similar balls may +be placed round it (all on the ground), so that they shall all touch +the central ball.</p> + +<p>As for the second question, the ratio of the diameter of a circle to +its circumference we call <i>pi</i>; and though we cannot express this +ratio in exact numbers, we can get sufficiently near to it for all +practical purposes. However, in this case it is not necessary to know +the value of <i>pi</i> at all. Because, to find the area of the surface of +a sphere we multiply the square of the diameter by <i>pi</i>; to find the +volume of a sphere we multiply the cube of the diameter by one-sixth +of <i>pi</i>. Therefore we may ignore <i>pi</i>, and have merely to seek a +number whose square shall equal one-sixth of its cube. This number is +obviously 6. Therefore the ball was 6 ft. in diameter, for the area of +its surface will be 36 times <i>pi</i> in square feet, and its volume also +36 times <i>pi</i> in cubic feet.</p> + +<hr style="width: 30%;" /> +<p><a name="X_189_THE_YORKSHIRE_ESTATESa" id="X_189_THE_YORKSHIRE_ESTATESa"></a><a href="#X_189_THE_YORKSHIRE_ESTATES"><b>189.—THE YORKSHIRE ESTATES.—<i>solution</i></b></a></p> + +<p>The triangular piece of land that was not for sale contains exactly +eleven acres. Of course it is not difficult to find the answer if we +follow the eccentric and tricky tracks of intricate trigonometry; or I +might say that the application of a well-known formula reduces the +problem to finding one-quarter of the square root of (4 × 370 × 116) - +(370 + 116 - 74)²—that is a quarter of the square root of 1936, which +is one-quarter of 44, or 11 acres. But all that the reader really +requires to know is the Pythagorean law on which many puzzles have +been built, that in any right-angled triangle the square of the +hypotenuse is equal to the sum of the squares of the other two sides. +I shall dispense with all "surds" and similar absurdities, +notwithstanding the fact that the sides of our triangle are clearly +incommensurate, since we cannot exactly extract the square roots of +the three square areas.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a189.png" width="400" height="235" alt="" title="" /> +</div> + +<p>In the above diagram ABC represents our triangle. ADB is a +right-angled triangle, AD measuring 9 and BD measuring 17, because the +square of 9 added to the square of 17 equals 370, the known area of +the square on AB. Also AEC is a right-angled triangle, and the square +of 5 added to the square of 7 equals 74, the square estate on A C. +Similarly, CFB is a right-angled triangle, for the square of 4 added +to the square of 10 equals 116, the square estate on BC. Now, although +the sides of our triangular estate are incommensurate, we have in this +diagram all the exact figures that we need to discover the area with +precision.</p> + +<p>The area of our triangle ADB is clearly half of 9 × 17, or 76½ acres. +The area of AEC is half of 5 × 7, or 17½ acres; the area of CFB is +half of 4 × 10, or 20 acres; and the area of the oblong EDFC is +obviously 4 × 7, or 28 acres. Now, if we add together 17½, 20, and <span class='pagenum'>Pg 184<a name="Page_184" id="Page_184"></a></span>28 += 65½, and deduct this sum from the area of the large triangle ADB +(which we have found to be 76½ acres), what remains must clearly be +the area of ABC. That is to say, the area we want must be 76½ - 65½ = +11 acres exactly.</p> + +<hr style="width: 30%;" /> +<p><a name="X_190_FARMER_WURZELS_ESTATEa" id="X_190_FARMER_WURZELS_ESTATEa"></a><a href="#X_190_FARMER_WURZELS_ESTATE"><b>190.—FARMER WURZEL'S ESTATE.—<i>solution</i></b></a></p> + +<p>The area of the complete estate is exactly one hundred acres. To find +this answer I use the following little formula,</p> + +<pre> + __________________ + \/4ab - (a + b - c)²; + _____________________ + 4 +</pre> + +<p>where a, b, c represent the three square areas, in any order. The +expression gives the area of the triangle A. This will be found to be +9 acres. It can be easily proved that A, B, C, and D are all equal in +area; so the answer is 26 + 20 + 18 + 9 + 9 + 9 + 9 = 100 acres.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a190.png" width="400" height="396" alt="" title="" /> +</div> + +<p>Here is the proof. If every little dotted square in the diagram +represents an acre, this must be a correct plan of the estate, for the +squares of 5 and 1 together equal 26; the squares of 4 and 2 equal 20; +and the squares of 3 and 3 added together equal 18. Now we see at once +that the area of the triangle E is 2½, F is 4½, and G is 4. These +added together make 11 acres, which we deduct from the area of the +rectangle, 20 acres, and we find that the field A contains exactly 9 +acres. If you want to prove that B, C, and D are equal in size to A, +divide them in two by a line from the middle of the longest side to +the opposite angle, and you will find that the two pieces in every +case, if cut out, will exactly fit together and form A.</p> + +<p>Or we can get our proof in a still easier way. The complete area of +the squared diagram is 12 × 12 = 144 acres, and the portions 1, 2, 3, +4, not included in the estate, have the respective areas of 12½, 17½, +9½, and 4½. These added together make 44, which, deducted from 144, +leaves 100 as the required area of the complete estate.</p> + +<hr style="width: 30%;" /> +<p><a name="X_191_THE_CRESCENT_PUZZLEa" id="X_191_THE_CRESCENT_PUZZLEa"></a><a href="#X_191_THE_CRESCENT_PUZZLE"><b>191.—THE CRESCENT PUZZLE.—<i>solution</i></b></a></p> + +<p>Referring to the original diagram, let AC be <i>x</i>, let CD be <i>x</i> - 9, and +let EC be <i>x</i> - 5. Then <i>x</i> - 5 is a mean proportional between <i>x</i> - 9 and +<i>x</i>, from which we find that <i>x</i> equals 25. Therefore the diameters are 50 +in. and 41 in. respectively.</p> + +<hr style="width: 30%;" /> +<p><a name="X_192_THE_PUZZLE_WALLa" id="X_192_THE_PUZZLE_WALLa"></a><a href="#X_192_THE_PUZZLE_WALL"><b>192.—THE PUZZLE WALL.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a192.png" width="400" height="300" alt="" title="" /> +</div> + +<p>The answer given in all the old books is that shown in Fig. 1, where +the curved wall shuts out the cottages from access to the lake. But in +seeking the direction for the "shortest possible" wall most readers +to-day, remembering that the shortest distance between two points is a +straight line, will adopt the method shown in Fig. 2. This is +certainly an improvement, yet the correct answer is really that +indicated in Fig. 3. A measurement of the lines will show that there +is a considerable saving of length in this wall.</p> + +<hr style="width: 30%;" /> +<p><a name="X_193_THE_SHEEP_FOLDa" id="X_193_THE_SHEEP_FOLDa"></a><a href="#X_193_THE_SHEEP_FOLD"><b>193.—THE SHEEP-FOLD.—<i>solution</i></b></a></p> + +<p>This is the answer that is always given and accepted as correct: Two +more hurdles would be necessary, for the pen was twenty-four by one +(as in Fig. A on next page), and by moving one of the sides and +placing an extra hurdle at each end (as in Fig. B) the area would be +doubled. The diagrams are not to scale. Now there is no condition in +the puzzle that requires the sheep-fold to be of any particular form. +But even if we accept the point that the pen was twenty-four by one, +the answer utterly fails, for two extra hurdles are certainly not at +all necessary. For example, I arrange the fifty hurdles as in Fig. C, +and as the area is increased from twenty-four "square hurdles" to 156, +there is now accommodation for 650 sheep. If it be held that the area +must be exactly double that of the original pen, then I construct it +(as in Fig. D) with twenty-eight hurdles only, and have twenty-two in +hand for other purposes on the farm. Even if it were insisted that all +the original hurdles must be used, then I should construct it as in +Fig. E, where I can get the area as exact as any farmer could possibly +require, even if we have to allow for the fact that the sheep might +not be able to graze at the extreme ends. Thus we see that, from any +<span class='pagenum'>Pg 185<a name="Page_185" id="Page_185"></a></span>point of view, the accepted answer to this ancient little puzzle +breaks down. And yet attention has never before been drawn to the +absurdity.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a193.png" width="400" height="473" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_194_THE_GARDEN_WALLSa" id="X_194_THE_GARDEN_WALLSa"></a><a href="#X_194_THE_GARDEN_WALLS"><b>194.—THE GARDEN WALLS.—<i>solution</i></b></a></p> + +<p>The puzzle was to divide the circular field into four equal parts by +three walls, each wall being of exactly the same length. There are two +essential difficulties in this problem. These are: (1) the thickness +of the walls, and (2) the condition that these walls are three in +number. As to the first point, since we are told that the walls are +brick walls, we clearly cannot ignore their thickness, while we have +to find a solution that will equally work, whether the walls be of a +thickness of one, two, three, or more bricks.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a194.png" width="400" height="412" alt="" title="" /> +</div> + +<p>The second point requires a little more consideration. How are we to +distinguish between a wall and walls? A straight wall without any bend +in it, no matter how long, cannot ever become "walls," if it is +neither broken nor intersected in any way. Also our circular field is +clearly enclosed by one wall. But if it had happened to be a square or +a triangular enclosure, would there be respectively four and three +walls or only one enclosing wall in each case? It is true that we +speak of "the four walls" of a square building or garden, but this is +only a conventional way of saying "the four sides." If you were +speaking of the actual brickwork, you would say, "I am going to +enclose this square garden with a wall." Angles clearly do not affect +the question, for we may have a zigzag wall just as well as a straight +one, and the Great Wall of China is a good example of a wall with +plenty of angles. Now, if you look at Diagrams 1, 2, and 3, you may be +puzzled to declare whether there are in each case two or four new +walls; but you cannot call them three, as required in our puzzle. The +intersection either affects the question or it does not affect it.</p> + +<p>If you tie two pieces of string firmly together, or splice them in a +nautical manner, they become "one piece of string." If you simply let +them lie across one another or overlap, they remain "two pieces of +string." It is all a question of joining and welding. It may similarly +be held that if two walls be built into one another—I might almost +say, if they be made homogeneous—they become one wall, in which case +Diagrams 1, 2, and 3 might each be said to show one wall or two, if it +be indicated that the four ends only touch, and are not really built +into, the outer circular wall.</p> + +<p>The objection to Diagram 4 is that although it shows the three +required walls (assuming the ends are not built into the outer +circular wall), yet it is only absolutely correct when we assume the +walls to have no thickness. A brick has thickness, and therefore the +fact throws the whole method out and renders it only approximately +correct.</p> + +<p>Diagram 5 shows, perhaps, the only correct and perfectly satisfactory +solution. It will be noticed that, in addition to the circular wall, +there are three new walls, which touch (and so enclose) but are not +built into one another. This solution may be adapted to any desired +thickness of wall, and its correctness as to area and length of wall +space is so obvious that it is unnecessary to explain it. I will, +however, just say that the semicircular piece of ground that each +tenant gives to his neighbour is exactly equal to the semicircular +piece that his neighbour gives to him, while any section of wall space +found in one garden is precisely repeated in all the others. Of course +there is an infinite number of ways in which this solution may be +correctly varied.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 186<a name="Page_186" id="Page_186"></a></span><a name="X_195_LADY_BELINDAS_GARDENa" id="X_195_LADY_BELINDAS_GARDENa"></a><a href="#X_195_LADY_BELINDAS_GARDEN"><b>195.—LADY BELINDA'S GARDEN.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a195.png" width="400" height="193" alt="" title="" /> +</div> + +<p>All that Lady Belinda need do was this: She should measure from A to +B, fold her tape in four and mark off the point E, which is thus one +quarter of the side. Then, in the same way, mark off the point F, +one-fourth of the side AD Now, if she makes EG equal to AF, and GH +equal to EF, then AH is the required width for the path in order that +the bed shall be exactly half the area of the garden. An exact +numerical measurement can only be obtained when the sum of the squares +of the two sides is a square number. Thus, if the garden measured 12 +poles by 5 poles (where the squares of 12 and 5, 144 and 25, sum to +169, the square of 13), then 12 added to 5, less 13, would equal four, +and a quarter of this, 1 pole, would be the width of the path.</p> + +<hr style="width: 30%;" /> +<p><a name="X_196_THE_TETHERED_GOATa" id="X_196_THE_TETHERED_GOATa"></a><a href="#X_196_THE_TETHERED_GOAT"><b>196.—THE TETHERED GOAT.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a196.png" width="400" height="370" alt="" title="" /> +</div> + +<p>This problem is quite simple if properly attacked. Let us suppose the +triangle ABC to represent our half-acre field, and the shaded portion +to be the quarter-acre over which the goat will graze when tethered to +the corner C. Now, as six equal equilateral triangles placed together +will form a regular hexagon, as shown, it is evident that the shaded +pasture is just one-sixth of the complete area of a circle. Therefore +all we require is the radius (CD) of a circle containing six +quarter-acres or 1½ acres, which is equal to 9,408,960 square +inches. As we only want our answer "to the nearest inch," it is +sufficiently exact for our purpose if we assume that as 1 is to +3.1416, so is the diameter of a circle to its circumference. If, +therefore, we divide the last number I gave by 3.1416, and extract the +square root, we find that 1,731 inches, or 48 yards 3 inches, is the +required length of the tether "to the nearest inch."</p> + +<hr style="width: 30%;" /> +<p><a name="X_197_THE_COMPASSES_PUZZLEa" id="X_197_THE_COMPASSES_PUZZLEa"></a><a href="#X_197_THE_COMPASSES_PUZZLE"><b>197.—THE COMPASSES PUZZLE.—<i>solution</i></b></a></p> + +<p>Let AB in the following diagram be the given straight line. With the +centres A and B and radius AB describe the two circles. Mark off DE +and EF equal to AD. With the centres A and F and radius DF describe +arcs intersecting at G. With the centres A and B and distance BG +describe arcs GHK and N. Make HK equal to AB and HL equal to HB. Then +with centres K and L and radius AB describe arcs intersecting at I. +Make BM equal to BI. Finally, with the centre M and radius MB cut the +line in C, and the point C is the required middle of the line AB. For +greater exactitude you can mark off R from A (as you did M from B), +and from R describe another arc at C. This also solves the problem, to +find a point midway between two given points without the straight +line.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a197.png" width="400" height="326" alt="" title="" /> +</div> + +<p>I will put the young geometer in the way of a rigid proof. First prove +that twice the square of the line AB equals the square of the distance +BG, from which it follows that HABN are the four corners of a square. +To prove that I is the centre of this square, draw a line from H to P +through QIB and continue the arc HK to P. Then, conceiving the +necessary lines to be drawn, the angle HKP, being in a semicircle, is +a right angle. Let fall the perpendicular KQ, and by similar +triangles, and from the fact that HKI is an isosceles triangle by the +construction, it can be proved that HI is half of HB. We can similarly +prove that C is the centre of the square of which AIB are three +corners.</p> + +<p>I am aware that this is not the simplest possible solution.</p> + +<hr style="width: 30%;" /> +<p><a name="X_198_THE_EIGHT_STICKSa" id="X_198_THE_EIGHT_STICKSa"></a><a href="#X_198_THE_EIGHT_STICKS"><b>198.—THE EIGHT STICKS.—<i>solution</i></b></a></p> + +<p>The first diagram is the answer that nearly every one will give to +this puzzle, and at first sight it seems quite satisfactory. But +consider the conditions. We have to lay "every one of the sticks on +the table." Now, if a ladder be <span class='pagenum'>Pg 187<a name="Page_187" id="Page_187"></a></span>placed against a wall with only one +end on the ground, it can hardly be said that it is "laid on the +ground." And if we place the sticks in the above manner, it is only +possible to make one end of two of them touch the table: to say that +every one lies on the table would not be correct. To obtain a solution +it is only necessary to have our sticks of proper dimensions. Say the +long sticks are each 2 ft. in length and the short ones 1 ft. Then the +sticks must be 3 in. thick, when the three equal squares may be +enclosed, as shown in the second diagram. If I had said "matches" +instead of "sticks," the puzzle would be impossible, because an +ordinary match is about twenty-one times as long as it is broad, and +the enclosed rectangles would not be squares.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a198.png" width="400" height="311" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_199_PAPAS_PUZZLEa" id="X_199_PAPAS_PUZZLEa"></a><a href="#X_199_PAPAS_PUZZLE"><b>199.—PAPA'S PUZZLE.—<i>solution</i></b></a></p> + +<p>I have found that a large number of people imagine that the following +is a correct solution of the problem. Using the letters in the diagram +below, they argue that if you make the distance BA one-third of BC, +and therefore the area of the rectangle ABE equal to that of the +triangular remainder, the card must hang with the long side +horizontal. Readers will remember the jest of Charles II., who induced +the Royal Society to meet and discuss the reason why the water in a +vessel will not rise if you put a live fish in it; but in the middle +of the proceedings one of the least distinguished among them quietly +slipped out and made the experiment, when he found that the water +<i>did</i> rise! If my correspondents had similarly made the experiment +with a piece of cardboard, they would have found at once their error. +Area is one thing, but gravitation is quite another. The fact of that +triangle sticking its leg out to D has to be compensated for by +additional area in the rectangle. As a matter of fact, the ratio of BA +to AC is as 1 is to the square root of 3, which latter cannot be given +in an exact numerical measure, but is approximately 1.732. Now let us +look at the correct general solution. There are many ways of arriving +at the desired result, but the one I give is, I think, the simplest +for beginners.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a199.png" width="400" height="342" alt="" title="" /> +</div> + +<p>Fix your card on a piece of paper and draw the equilateral triangle +BCF, BF and CF being equal to BC. Also mark off the point G so that DG +shall equal DC. Draw the line CG and produce it until it cuts the line +BF in H. If we now make HA parallel to BE, then A is the point from +which our cut must be made to the corner D, as indicated by the dotted +line.</p> + +<p>A curious point in connection with this problem is the fact that the +position of the point A is independent of the side CD. The reason for +this is more obvious in the solution I have given than in any other +method that I have seen, and (although the problem may be solved with +all the working on the cardboard) that is partly why I have preferred +it. It will be seen at once that however much you may reduce the width +of the card by bringing E nearer to B and D nearer to C, the line CG, +being the diagonal of a square, will always lie in the same direction, +and will cut BF in H. Finally, if you wish to get an approximate +measure for the distance BA, all you have to do is to multiply the +length of the card by the decimal .366. Thus, if the card were 7 +inches long, we get 7 × .366 = 2.562, or a little more than 2½ inches, for +the distance from B to A.</p> + +<p>But the real joke of the puzzle is this: We have seen that the +position of the point A is independent of the width of the card, and +depends entirely on the length. Now, in the illustration it will be +found that both cards have the same length; consequently all the +little maid had to do was to lay the clipped card on top of the other +one and mark off the point A at precisely the same distance from the +top left-hand corner! So, after all, Pappus' puzzle, as he presented +it to his little maid, was quite an infantile problem, when he was +able to show her how to perform the feat without first introducing her +to the elements of statics and geometry.</p> + +<hr style="width: 30%;" /> +<p><a name="X_200_A_KITE-FLYING_PUZZLEa" id="X_200_A_KITE-FLYING_PUZZLEa"></a><a href="#X_200_A_KITE-FLYING_PUZZLE"><b>200.—A KITE-FLYING PUZZLE.—<i>solution</i></b></a></p> + +<p>Solvers of this little puzzle, I have generally found, may be roughly +divided into two classes: those who get within a mile of the correct +answer by means of more or less complex calcu<span class='pagenum'>Pg 188<a name="Page_188" id="Page_188"></a></span>lations, involving +"<i>pi</i>," and those whose arithmetical kites fly hundreds and thousands +of miles away from the truth. The comparatively easy method that I +shall show does not involve any consideration of the ratio that the +diameter of a circle bears to its circumference. I call it the +"hat-box method."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a200.png" width="400" height="469" alt="" title="" /> +</div> + +<p>Supposing we place our ball of wire, A, in a cylindrical hat-box, B, +that exactly fits it, so that it touches the side all round and +exactly touches the top and bottom, as shown in the illustration. +Then, by an invariable law that should be known by everybody, that box +contains exactly half as much again as the ball. Therefore, as the +ball is 24 in. in diameter, a hat-box of the same circumference but +two-thirds of the height (that is, 16 in. high) will have exactly the +same contents as the ball.</p> + +<p>Now let us consider that this reduced hat-box is a cylinder of metal +made up of an immense number of little wire cylinders close together +like the hairs in a painter's brush. By the conditions of the puzzle +we are allowed to consider that there are no spaces between the wires. +How many of these cylinders one one-hundredth of an inch thick are +equal to the large cylinder, which is 24 in. thick? Circles are to one +another as the squares of their diameters. The square of <sup>1</sup>/<sub>100</sub> is +<sup>1</sup>/<sub>100000</sub>, and the square of 24 is 576; therefore the large cylinder +contains 5,760,000 of the little wire cylinders. But we have seen that +each of these wires is 16 in. long; hence 16 × 5,760,000 = 92,160,000 +inches as the complete length of the wire. Reduce this to miles, and +we get 1,454 miles 2,880 ft. as the length of the wire attached to the +professor's kite.</p> + +<p>Whether a kite would fly at such a height, or support such a weight, +are questions that do not enter into the problem.</p> + +<hr style="width: 30%;" /> +<p><a name="X_201_HOW_TO_MAKE_CISTERNSa" id="X_201_HOW_TO_MAKE_CISTERNSa"></a><a href="#X_201_HOW_TO_MAKE_CISTERNS"><b>201.—HOW TO MAKE CISTERNS.—<i>solution</i></b></a></p> + +<p>Here is a general formula for solving this problem. Call the two sides +of the rectangle <i>a</i> and <i>b</i>. Then</p> + +<div style="font-size: larger;"> +<p class='center'><span class='su2'>( <i>a</i> + <i>b</i> - (<i>a</i><sup>2</sup> + <i>b</i><sup>2</sup> - <i>ab</i>)<sup>½</sup> )</span>/<sub>6</sub></p> +</div> + +<p>equals the side of the little square pieces to cut away. The measurements given +were 8 ft. by 3 ft., and the above rule gives 8 in. as the side of the +square pieces that have to be cut away. Of course it will not always +come out exact, as in this case (on account of that square root), but +you can get as near as you like with decimals.</p> + +<hr style="width: 30%;" /> +<p><a name="X_202_THE_CONE_PUZZLEa" id="X_202_THE_CONE_PUZZLEa"></a><a href="#X_202_THE_CONE_PUZZLE"><b>202.—THE CONE PUZZLE.—<i>solution</i></b></a></p> + +<p>The simple rule is that the cone must be cut at one-third of its +altitude.</p> + +<hr style="width: 30%;" /> +<p><a name="X_203_CONCERNING_WHEELSa" id="X_203_CONCERNING_WHEELSa"></a><a href="#X_203_CONCERNING_WHEELS"><b>203.—CONCERNING WHEELS.—<i>solution</i></b></a></p> + +<p>If you mark a point A on the circumference of a wheel that runs on the +surface of a level road, like an ordinary cart-wheel, the curve +described by that point will be a common cycloid, as in Fig. 1. But if +you mark a point B on the circumference of the flange of a +locomotive-wheel, the curve will be a curtate cycloid, as in Fig. 2, +terminating in nodes. Now, if we consider one of these nodes or loops, +we shall see that "at any given moment" certain points at the bottom +of the loop must be moving in the opposite direction to the train. As +there is an infinite number of such points on the flange's +circumference, there must be an infinite number of these loops being +described while the train is in motion. In fact, at any given moment +certain points on the flanges are always moving in a direction +opposite to that in which the train is going.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a203.png" width="400" height="305" alt="" title="" /> +</div> + +<p>In the case of the two wheels, the wheel that runs round the +stationary one makes two revolutions round its own centre. As both +wheels are of the same size, it is obvious that if at the start we +mark a point on the circumference of the upper wheel, at the very top, +this point will be in contact with the lower wheel at its lowest part +when half the journey has been made. Therefore this point is again at +the top of the moving wheel, and one revolution has been made. +Consequently there are two such revolutions in the complete journey.</p> + +<hr style="width: 30%;" /> +<p><a name="X_204_A_NEW_MATCH_PUZZLEa" id="X_204_A_NEW_MATCH_PUZZLEa"></a><a href="#X_204_A_NEW_MATCH_PUZZLE"><b>204.—A NEW MATCH PUZZLE.—<i>solution</i></b></a></p> + +<p>1. The easiest way is to arrange the eighteen matches as in Diagrams 1 +and 2, making the length of the perpendicular AB equal to a match and +a half. Then, if the matches are an inch in <span class='pagenum'>Pg 189<a name="Page_189" id="Page_189"></a></span>length, Fig. 1 contains +two square inches and Fig. 2 contains six square inches—4 × 1½. The +second case (2) is a little more difficult to solve. The solution is +given in Figs. 3 and 4. For the purpose of construction, place matches +temporarily on the dotted lines. Then it will be seen that as 3 +contains five equal equilateral triangles and 4 contains fifteen +similar triangles, one figure is three times as large as the other, +and exactly eighteen matches are used.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a204.png" width="400" height="339" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_205_THE_SIX_SHEEP-PENSa" id="X_205_THE_SIX_SHEEP-PENSa"></a><a href="#X_205_THE_SIX_SHEEP-PENS"><b>205.—THE SIX SHEEP-PENS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/a205.png" width="300" height="274" alt="" title="" /> +</div> + +<p>Place the twelve matches in the manner shown in the +illustration, and you will have six pens of equal size.</p> + +<hr style="width: 30%;" /> +<p><a name="X_206_THE_KING_AND_THE_CASTLESa" id="X_206_THE_KING_AND_THE_CASTLESa"></a><a href="#X_206_THE_KING_AND_THE_CASTLES"><b>206.—THE KING AND THE CASTLES.—<i>solution</i></b></a></p> + +<p>There are various ways of building the ten castles so that they shall +form five rows with four castles in every row, but the arrangement in +the next column is the only one that also provides that two castles +(the greatest number possible) shall not be approachable from the +outside. It will be seen that you must cross the walls to reach these +two.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a206.png" width="400" height="565" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_207_CHERRIES_AND_PLUMSa" id="X_207_CHERRIES_AND_PLUMSa"></a><a href="#X_207_CHERRIES_AND_PLUMS"><b>207.—CHERRIES AND PLUMS.—<i>solution</i></b></a></p> + +<p>There are several ways in which this problem might be solved were it +not for the condition that as few cherries and plums as possible shall +be planted on the north and east sides of the orchard. The best +possible arrangement is that shown in the diagram, where the cherries, +plums, and apples are indicated respectively by the letters C, P, and +A. The dotted lines connect the cherries, and the other lines the +plums. It will be seen that the ten cherry trees and the ten plum +trees are so planted that each fruit forms five lines with four trees +of its kind in line. This is the only arrangement that allows of so +few as two cherries or plums being planted on the north and east +outside rows.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a207.png" width="400" height="388" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_208_A_PLANTATION_PUZZLEa" id="X_208_A_PLANTATION_PUZZLEa"></a><a href="#X_208_A_PLANTATION_PUZZLE"><b>208.—A PLANTATION PUZZLE.—<i>solution</i></b></a></p> + +<p>The illustration shows the ten trees that must be left to form five +rows with four trees in every <span class='pagenum'>Pg 190<a name="Page_190" id="Page_190"></a></span>row. The dots represent the positions +of the trees that have been cut down.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a208.png" width="400" height="402" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_209_THE_TWENTY-ONE_TREESa" id="X_209_THE_TWENTY-ONE_TREESa"></a><a href="#X_209_THE_TWENTY-ONE_TREES"><b>209.—THE TWENTY-ONE TREES.—<i>solution</i></b></a></p> + +<p>I give two pleasing arrangements of the trees. In each case there are +twelve straight rows with five trees in every row.</p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/a209a.png" width="300" height="302" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 300px;"> +<img src="images/a209b.png" width="300" height="291" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_210_THE_TEN_COINSa" id="X_210_THE_TEN_COINSa"></a><a href="#X_210_THE_TEN_COINS"><b>210.—THE TEN COINS.—<i>solution</i></b></a></p> + +<p>The answer is that there are just 2,400 different ways. Any three +coins may be taken from one side to combine with one coin taken from +the other side. I give four examples on this and the next page. We may +thus select three from the top in ten ways and one from the bottom in +five ways, making fifty. But we may also select three from the bottom +and one from the top in fifty ways. We may thus select the four coins +in one hundred ways, and the four removed may be arranged by +permutation in twenty-four ways. Thus there are 24 × 100 = 2,400 +different solutions.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a210a.png" width="400" height="390" alt="" title="" /> +</div> + + +<p>As all the points and lines puzzles that I have given so far, +excepting the last, are variations of the case of ten points arranged +to form five lines of four, it will be well to consider this +particular case generally. There are six fundamental solutions, and no +more, as shown in the six diagrams. These, for the sake of +convenience, I named some years ago the Star, the Dart, the Compasses, +the Funnel, the Scissors, and the Nail. (See next page.) Readers will +understand that any one of these forms may be distorted in an infinite +number of different ways without destroying its real character.</p> + +<p>In "The King and the Castles" we have the Star, and its solution gives +the Compasses. In the "Cherries and Plums" solution we find that the +Cherries represent the Funnel and the Plums the Dart. The solution of +the "Plantation Puzzle" is an example of the Dart distorted. Any +solution to the "Ten Coins" will represent the Scissors. Thus examples +of all have been given except the Nail.</p> + +<p><span class='pagenum'>Pg 191<a name="Page_191" id="Page_191"></a></span></p><div class="figcenter" style="width: 600px;"> +<img src="images/a210b.png" width="600" height="164" alt="" title="" /> +</div> + +<p>On a reduced chessboard, 7 by 7, we may place the ten pawns in just +three different ways, but they must all represent the Dart. The +"Plantation" shows one way, the Plums show a second way, and the +reader may like to find the third way for himself. On an ordinary +chessboard, 8 by 8, we can also get in a beautiful example of the +Funnel—symmetrical in relation to the diagonal of the board. The +smallest board that will take a Star is one 9 by 7. The Nail requires +a board 11 by 7, the Scissors 11 by 9, and the Compasses 17 by 12. At least these are the best +results recorded in my note-book. They may be beaten, but I do not +think so. If you divide a chessboard into two parts by a diagonal +zigzag line, so that the larger part contains 36 squares and the +smaller part 28 squares, you can place three separate schemes on the +larger part and one on the smaller part (all Darts) without their +conflicting—that is, they occupy forty different squares. They can be +placed in other ways without a division of the board. The smallest +square board that will contain six different schemes (not +fundamentally different), without any line of one scheme crossing the +line of another, is 14 by 14; and the smallest board that will contain +one scheme entirely enclosed within the lines of a second scheme, +without any of the lines of the one, when drawn from point to point, +crossing a line of the other, is 14 by 12.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a210c.png" width="600" height="131" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_211_THE_TWELVE_MINCE-PIESa" id="X_211_THE_TWELVE_MINCE-PIESa"></a><a href="#X_211_THE_TWELVE_MINCE-PIES"><b>211.—THE TWELVE MINCE-PIES.—<i>solution</i></b></a></p> + +<p>If you ignore the four black pies in our illustration, the remaining +twelve are in their original positions. Now remove the four detached +pies to the places occupied by the black ones, and you will have your +seven straight rows of four, as shown by the dotted lines.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a211.png" width="400" height="502" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_212_THE_BURMESE_PLANTATIONa" id="X_212_THE_BURMESE_PLANTATIONa"></a><a href="#X_212_THE_BURMESE_PLANTATION"><b>212.—THE BURMESE PLANTATION.—<i>solution</i></b></a></p> + +<p>The arrangement on the next page is the most symmetrical answer that +can probably be found for twenty-one rows, which is, I believe, the +greatest number of rows possible. There are several ways of doing it.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a212.png" width="400" height="413" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_213_TURKS_AND_RUSSIANSa" id="X_213_TURKS_AND_RUSSIANSa"></a><a href="#X_213_TURKS_AND_RUSSIANS"><b>213.—TURKS AND RUSSIANS.—<i>solution</i></b></a></p> + +<p>The main point is to discover the smallest possible number of Russians +that there could have been. As the enemy opened fire from all +directions, it is clearly necessary to find what is the smallest +number of heads that could form sixteen lines with three heads in +every line. Note that I say sixteen, and not thirty-two, because every +line taken by a bullet may be also taken by another bullet fired in +exactly the opposite direction. Now, as few as eleven points, or +heads, may be arranged to form the required sixteen lines of three, +but the discovery of this arrangement is a hard nut. The diagram<span class='pagenum'>Pg 192<a name="Page_192" id="Page_192"></a></span> +at the foot of this page will show exactly how the thing is to be +done.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a213.png" width="400" height="398" alt="" title="" /> +</div> + +<p>If, therefore, eleven Russians were in the positions shown by the +stars, and the thirty-two Turks in the positions indicated by the +black dots, it will be seen, by the lines shown, that each Turk may +fire exactly over the heads of three Russians. But as each bullet +kills a man, it is essential that every Turk shall shoot one of his +comrades and be shot by him in turn; otherwise we should have to +provide extra Russians to be shot, which would be destructive of the +correct solution of our problem. As the firing was simultaneous, this +point presents no difficulties. The answer we thus see is that there +were at least eleven Russians amongst whom there was no casualty, and +that all the thirty-two Turks were shot by one another. It was not +stated whether the Russians fired any shots, but it will be evident +that even if they did their firing could not have been effective: for +if one of their bullets killed a Turk, then we have immediately to +provide another man for one of the Turkish bullets to kill; and as the +Turks were known to be thirty-two in number, this <span class='pagenum'>Pg 193<a name="Page_193" id="Page_193"></a></span>would necessitate +our introducing another Russian soldier and, of course, destroying the +solution. I repeat that the difficulty of the puzzle consists in +finding how to arrange eleven points so that they shall form sixteen +lines of three. I am told that the possibility of doing this was first +discovered by the Rev. Mr. Wilkinson some twenty years ago.</p> + +<hr style="width: 30%;" /> +<p><a name="X_214_THE_SIX_FROGSa" id="X_214_THE_SIX_FROGSa"></a><a href="#X_214_THE_SIX_FROGS"><b>214.—THE SIX FROGS.—<i>solution</i></b></a></p> + +<p>Move the frogs in the following order: 2, 4, 6, 5, 3, 1 (repeat these +moves in the same order twice more), 2, 4, 6. This is a solution in +twenty-one moves—the fewest possible.</p> + +<p>If <i>n</i>, the number of frogs, be even, we require <sup>(<i>n</i>²+<i>n</i>)</sup>/<sub>2</sub> moves, +of which <sup>(<i>n</i>²-<i>n</i>)</sup>/<sub>2</sub> will be leaps and <i>n</i> simple moves. If <i>n</i> be +odd, we shall need (<sup>(<i>n</i>²+3<i>n</i>)</sup>/<sub>2</sub>)-4 moves, of which <sup>(<i>n</i>²-<i>n</i>)</sup>/<sub>2</sub> will +be leaps and 2<i>n</i>-4 simple moves.</p> + +<p>In the even cases write, for the moves, all the even numbers in +ascending order and the odd numbers in descending order. This series +must be repeated ½<i>n</i> times and followed by the even numbers in +ascending order once only. Thus the solution for 14 frogs will be (2, +4, 6, 8, 10, 12, 14, 13, 11, 9, 7, 5, 3, 1) repeated 7 times and +followed by 2, 4, 6, 8, 10, 12, 14 = 105 moves.</p> + +<p>In the odd cases, write the even numbers in ascending order and the +odd numbers in descending order, repeat this series ½(<i>n</i>-1) times, +follow with the even numbers in ascending order (omitting <i>n</i>-1), the +odd numbers in descending order (omitting 1), and conclude with all +the numbers (odd and even) in their natural order (omitting 1 and +<i>n</i>). Thus for 11 frogs: (2, 4, 6, 8, 10, 11, 9, 7, 5, 3, 1) repeated +5 times, 2, 4, 6, 8, 11, 9, 7, 5, 3, and 2, 3, 4, 5, 6, 7, 8, 9, 10 = +73 moves.</p> + +<p>This complete general solution is published here for the first time.</p> + +<hr style="width: 30%;" /> +<p><a name="X_215_THE_GRASSHOPPER_PUZZLEa" id="X_215_THE_GRASSHOPPER_PUZZLEa"></a><a href="#X_215_THE_GRASSHOPPER_PUZZLE"><b>215.—THE GRASSHOPPER PUZZLE.—<i>solution</i></b></a></p> + +<p>Move the counters in the following order. The moves in brackets are to +be made four times in succession. 12, 1, 3, 2, 12, 11, 1, 3, 2 (5, 7, +9, 10, 8, 6, 4), 3, 2, 12, 11, 2, 1, 2. The grasshoppers will then be +reversed in forty-four moves.</p> + +<p>The general solution of this problem is very difficult. Of course it +can always be solved by the method given in the solution of the last +puzzle, if we have no desire to use the fewest possible moves. But to +employ a full economy of moves we have two main points to consider. +There are always what I call a lower movement (L) and an upper +movement (U). L consists in exchanging certain of the highest numbers, +such as 12, 11, 10 in our "Grasshopper Puzzle," with certain of the +lower numbers, 1, 2, 3; the former moving in a clockwise direction, +the latter in a non-clockwise direction. U consists in reversing the +intermediate counters. In the above solution for 12, it will be seen +that 12, 11, and 1, 2, 3 are engaged in the L movement, and 4, 5, 6, +7, 8, 9, 10 in the U movement. The L movement needs 16 moves and U 28, +making together 44. We might also involve 10 in the L movement, which +would result in L 23, U 21, making also together 44 moves. These I +call the first and second methods. But any other scheme will entail an +increase of moves. You always get these two methods (of equal economy) +for odd or even counters, but the point is to determine just how many +to involve in L and how many in U. Here is the solution in table form. +But first note, in giving values to <i>n</i>, that 2, 3, and 4 counters are +special cases, requiring respectively 3, 3, and 6 moves, and that 5 +and 6 counters do not give a minimum solution by the second +method—only by the first.</p> + +<h5>FIRST METHOD.</h5> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' rowspan='2'>Total No.<br />of<br />Counters.</td><td align='center' colspan='2'>L MOVEMENT.</td><td align='center' colspan='2'>U MOVEMENT. </td><td align='center' rowspan='2'>Total No.<br />of Moves.</td></tr> +<tr><td align='center'>No. of <br />Counters.</td><td align='center'>No. of <br />Moves.</td><td align='center'>No. of <br />Counters.</td><td align='center'>No. of <br />Moves.</td></tr> +<tr><td align='center'>4n</td><td align='center'>n - 1 and n</td><td align='center'>2(n - 1)² + 5n - 7</td><td align='center'>2n + 1</td><td align='center'>2n² + 3n + 1</td><td align='center'>4(n² + n - 1)</td></tr> +<tr><td align='center'>4n - 2</td><td align='center'>n - 1 " n</td><td align='center'>2(n - 1)² + 5n - 7</td><td align='center'>2n - 1</td><td align='center'>2(n - 1)² + 3n - 2</td><td align='center'>4n² - 5</td></tr> +<tr><td align='center'>4n + 1</td><td align='center'>n " n + 1</td><td align='center'>2n² + 5n - 2</td><td align='center'>2n</td><td align='center'>2n² + 3n - 4</td><td align='center'>2(2n² + 4n - 3)</td></tr> +<tr><td align='center'>4n - 1</td><td align='center'>n - 1 " n</td><td align='center'>2(n - 1)² + 5n - 7</td><td align='center'>2n</td><td align='center'>2n² + 3n - 4</td><td align='center'>4n² + 4n - 9</td></tr> +</table></div> + +<h5>SECOND METHOD.</h5> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' rowspan='2'>Total No.<br />of<br />Counters.</td><td align='center' colspan='2'>L MOVEMENT.</td><td align='center' colspan='2'>U MOVEMENT. </td><td align='center' rowspan='2'>Total No.<br />of Moves.</td></tr> +<tr><td align='center'>No. of <br />Counters.</td><td align='center'>No. of <br />Moves.</td><td align='center'>No. of <br />Counters.</td><td align='center'>No. of <br />Moves.</td></tr> +<tr><td align='center'>4n</td><td align='center'>n and n</td><td align='center'>2n² + 3n - 4</td><td align='center'>2n</td><td align='center'>2(n - 1)² + 5n - 2</td><td align='center'>4(n² + n - 1)</td></tr> +<tr><td align='center'>4n - 2</td><td align='center'>n - 1 " n - 1</td><td align='center'>2(n - 1)² + 3n - 7</td><td align='center'>2n</td><td align='center'>2(n - 1)² + 5n - 2</td><td align='center'>4n² - 5</td></tr> +<tr><td align='center'>4n + 1</td><td align='center'>n " n</td><td align='center'>2n² + 3n - 4</td><td align='center'>2n + 1</td><td align='center'>2n² + 5n - 2</td><td align='center'>2(2n² + 4n - 3)</td></tr> +<tr><td align='center'>4n - 1</td><td align='center'>n " n</td><td align='center'>2n² + 3n - 4</td><td align='center'>2n - 1</td><td align='center'>2(n - 1)² + 5n - 7</td><td align='center'>4n² + 4n-9</td></tr> +</table></div> + +<p><span class='pagenum'>Pg 194<a name="Page_194" id="Page_194"></a></span>More generally we may say that with <i>m</i> counters, where <i>m</i> is even +and greater than 4, we require <sup>(m² + 4m - 16)</sup>/<sub>4</sub> moves; and where <i>m</i> is +odd and greater than 3, <sup>(m² + 6m - 31)</sup>/<sub>4</sub> moves. I have thus shown the +reader how to find the minimum number of moves for any case, and the +character and direction of the moves. I will leave him to discover for +himself how the actual order of moves is to be determined. This is a +hard nut, and requires careful adjustment of the L and the U +movements, so that they may be mutually accommodating.</p> + +<hr style="width: 30%;" /> +<p><a name="X_216_THE_EDUCATED_FROGSa" id="X_216_THE_EDUCATED_FROGSa"></a><a href="#X_216_THE_EDUCATED_FROGS"><b>216.—THE EDUCATED FROGS.—<i>solution</i></b></a></p> + +<p>The following leaps solve the puzzle in ten moves: 2 to 1, 5 to 2, 3 +to 5, 6 to 3, 7 to 6, 4 to 7, 1 to 4, 3 to 1, 6 to 3, 7 to 6.</p> + +<hr style="width: 30%;" /> +<p><a name="X_217_THE_TWICKENHAM_PUZZLEa" id="X_217_THE_TWICKENHAM_PUZZLEa"></a><a href="#X_217_THE_TWICKENHAM_PUZZLE"><b>217.—THE TWICKENHAM PUZZLE.—<i>solution</i></b></a></p> + +<p>Play the counters in the following order: K C E K W T C E H M K W T A +N C E H M I K C E H M T, and there you are, at Twickenham. The +position itself will always determine whether you are to make a leap +or a simple move.</p> + +<hr style="width: 30%;" /> +<p><a name="X_218_THE_VICTORIA_CROSS_PUZZLEa" id="X_218_THE_VICTORIA_CROSS_PUZZLEa"></a><a href="#X_218_THE_VICTORIA_CROSS_PUZZLE"><b>218.—THE VICTORIA CROSS PUZZLE.—<i>solution</i></b></a></p> + +<p>In solving this puzzle there were two things to be achieved: first, so +to manipulate the counters that the word VICTORIA should read round +the cross in the same direction, only with the V on one of the dark +arms; and secondly, to perform the feat in the fewest possible moves. +Now, as a matter of fact, it would be impossible to perform the first +part in any way whatever if all the letters of the word were +different; but as there are two I's, it can be done by making these +letters change places—that is, the first I changes from the 2nd place +to the 7th, and the second I from the 7th place to the 2nd. But the +point I referred to, when introducing the puzzle, as a little +remarkable is this: that a solution in twenty-two moves is obtainable +by moving the letters in the order of the following words: "A VICTOR! +A VICTOR! A VICTOR I!"</p> + +<p>There are, however, just six solutions in eighteen moves, and the +following is one of them: I (1), V, A, I (2), R, O, T, I (1), I (2), +A, V, I (2), I (1), C, I (2), V, A, I (1). The first and second I in +the word are distinguished by the numbers 1 and 2.</p> + +<p>It will be noticed that in the first solution given above one of the +I's never moves, though the movements of the other letters cause it to +change its relative position. There is another peculiarity I may point +out—that there is a solution in twenty-eight moves requiring no +letter to move to the central division except the I's. I may also +mention that, in each of the solutions in eighteen moves, the letters +C, T, O, R move once only, while the second I always moves four times, +the V always being transferred to the right arm of the cross.</p> + +<hr style="width: 30%;" /> +<p><a name="X_219_THE_LETTER_BLOCK_PUZZLEa" id="X_219_THE_LETTER_BLOCK_PUZZLEa"></a><a href="#X_219_THE_LETTER_BLOCK_PUZZLE"><b>219.—THE LETTER BLOCK PUZZLE.—<i>solution</i></b></a></p> + +<p>This puzzle can be solved in 23 moves—the fewest possible. Move the +blocks in the following order: A, B, F, E, C, A, B, F, E, C, A, B, D, +H, G, A, B, D, H, G, D, E, F.</p> + +<hr style="width: 30%;" /> +<p><a name="X_220_A_LODGING-HOUSE_DIFFICULTYa" id="X_220_A_LODGING-HOUSE_DIFFICULTYa"></a><a href="#X_220_A_LODGING-HOUSE_DIFFICULTY"><b>220.—A LODGING-HOUSE DIFFICULTY.—<i>solution</i></b></a></p> + +<p>The shortest possible way is to move the articles in the following +order: Piano, bookcase, wardrobe, piano, cabinet, chest of drawers, +piano, wardrobe, bookcase, cabinet, wardrobe, piano, chest of drawers, +wardrobe, cabinet, bookcase, piano. Thus seventeen removals are +necessary. The landlady could then move chest of drawers, wardrobe, +and cabinet. Mr. Dobson did not mind the wardrobe and chest of drawers +changing rooms so long as he secured the piano.</p> + +<hr style="width: 30%;" /> +<p><a name="X_221_THE_EIGHT_ENGINESa" id="X_221_THE_EIGHT_ENGINESa"></a><a href="#X_221_THE_EIGHT_ENGINES"><b>221.—THE EIGHT ENGINES.—<i>solution</i></b></a></p> + +<p>The solution to the Eight Engines Puzzle is as follows: The engine +that has had its fire drawn and therefore cannot move is No. 5. Move +the other engines in the following order: 7, 6, 3, 7, 6, 1, 2, 4, 1, +3, 8, 1, 3, 2, 4, 3, 2, seventeen moves in all, leaving the eight +engines in the required order.</p> + +<p>There are two other slightly different solutions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_222_A_RAILWAY_PUZZLEa" id="X_222_A_RAILWAY_PUZZLEa"></a><a href="#X_222_A_RAILWAY_PUZZLE"><b>222.—A RAILWAY PUZZLE.—<i>solution</i></b></a></p> + +<p>This little puzzle may be solved in as few as nine moves. Play the +engines as follows: From 9 to 10, from 6 to 9, from 5 to 6, from 2 to +5, from 1 to 2, from 7 to 1, from 8 to 7, from 9 to 8, and from 10 to +9. You will then have engines A, B, and C on each of the three circles +and on each of the three straight lines. This is the shortest solution +that is possible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_223_A_RAILWAY_MUDDLEa" id="X_223_A_RAILWAY_MUDDLEa"></a><a href="#X_223_A_RAILWAY_MUDDLE"><b>223.—A RAILWAY MUDDLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a223.png" width="400" height="325" alt="" title="" /> +</div> + +<p>Only six reversals are necessary. The white train (from A to D) is +divided into three sections, engine and 7 wagons, 8 wagons, and 1 +wagon. The black train (D to A) never uncouples anything throughout. +Fig. 1 is original position <span class='pagenum'>Pg 195<a name="Page_195" id="Page_195"></a></span>with 8 and 1 uncoupled. The black train +proceeds to position in Fig. 2 (no reversal). The engine and 7 proceed +towards D, and black train backs, leaves 8 on loop, and takes up +position in Fig. 3 (first reversal). Black train goes to position in +Fig. 4 to fetch single wagon (second reversal). Black train pushes 8 +off loop and leaves single wagon there, proceeding on its journey, as +in Fig. 5 (third and fourth reversals). White train now backs on to +loop to pick up single car and goes right away to D (fifth and sixth +reversals).</p> + +<hr style="width: 30%;" /> +<p><a name="X_224_THE_MOTOR-GARAGE_PUZZLEa" id="X_224_THE_MOTOR-GARAGE_PUZZLEa"></a><a href="#X_224_THE_MOTOR-GARAGE_PUZZLE"><b>224.—THE MOTOR-GARAGE PUZZLE.—<i>solution</i></b></a></p> + +<p>The exchange of cars can be made in forty-three moves, as follows: +6-G, 2-B, 1-E, 3-H, 4-I, 3-L, 6-K, 4-G, 1-I, 2-J, 5-H, 4-A, 7-F, 8-E, +4-D, 8-C, 7-A, 8-G, 5-C, 2-B, 1-E, 8-I, 1-G, 2-J, 7-H, 1-A, 7-G, 2-B, +6-E, 3-H, 8-L, 3-I, 7-K, 3-G, 6-I, 2-J, 5-H, 3-C, 5-G, 2-B, 6-E, 5-I, +6-J. Of course, "6-G" means that the car numbered "6" moves to the +point "G." There are other ways in forty-three moves.</p> + +<hr style="width: 30%;" /> +<p><a name="X_225_THE_TEN_PRISONERSa" id="X_225_THE_TEN_PRISONERSa"></a><a href="#X_225_THE_TEN_PRISONERS"><b>225.—THE TEN PRISONERS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a225.png" width="400" height="394" alt="" title="" /> +</div> + +<p>It will be seen in the illustration how the prisoners may be arranged +so as to produce as many as sixteen even rows. There are 4 such +vertical rows, 4 horizontal rows, 5 diagonal rows in one direction, +and 3 diagonal rows in the other direction. The arrows here show the +movements of the four prisoners, and it will be seen that the infirm +man in the bottom corner has not been moved.</p> + +<hr style="width: 30%;" /> +<p><a name="X_226_ROUND_THE_COASTa" id="X_226_ROUND_THE_COASTa"></a><a href="#X_226_ROUND_THE_COAST"><b>226.—ROUND THE COAST.—<i>solution</i></b></a></p> + +<p>In order to place words round the circle under the conditions, it is +necessary to select words in which letters are repeated in certain +relative positions. Thus, the word that solves our puzzle is +"Swansea," in which the first and fifth letters are the same, and the +third and seventh the same. We make out jumps as follows, taking the +letters of the word in their proper order: 2-5, 7-2, 4-7, 1-4, 6-1, +3-6, 8-3. Or we could place a word like "Tarapur" (in which the second +and fourth letters, and the third and seventh, are alike) with these +moves: 6-1, 7-4, 2-7, 5-2, 8-5, 3-6, 8-3. But "Swansea" is the only +word, apparently, that will fulfil the conditions of the puzzle.</p> + +<p>This puzzle should be compared with Sharp's Puzzle, referred to in my +solution to No. 341, "The Four Frogs." The condition "touch and jump +over two" is identical with "touch and move along a line."</p> + +<hr style="width: 30%;" /> +<p><a name="X_227_CENTRAL_SOLITAIREa" id="X_227_CENTRAL_SOLITAIREa"></a><a href="#X_227_CENTRAL_SOLITAIRE"><b>227.—CENTRAL SOLITAIRE.—<i>solution</i></b></a></p> + +<p>Here is a solution in nineteen moves; the moves enclosed in brackets +count as one move only: 19-17, 16-18, (29-17, 17-19), 30-18, 27-25, +(22-24, 24-26), 31-23, (4-16, 16-28), 7-9, 10-8, 12-10, 3-11, 18-6, +(1-3, 3-11), (13-27, 27-25), (21-7, 7-9), (33-31, 31-23), (10-8, 8-22, +22-24, 24-26, 26-12, 12-10), 5-17. All the counters are now removed +except one, which is left in the central hole. The solution needs +judgment, as one is tempted to make several jumps in one move, where +it would be the reverse of good play. For example, after playing the +first 3-11 above, one is inclined to increase the length of the move +by continuing with 11-25, 25-27, or with 11-9, 9-7.</p> + +<p>I do not think the number of moves can be reduced.</p> + +<hr style="width: 30%;" /> +<p><a name="X_228_THE_TEN_APPLESa" id="X_228_THE_TEN_APPLESa"></a><a href="#X_228_THE_TEN_APPLES"><b>228.—THE TEN APPLES.—<i>solution</i></b></a></p> + +<p>Number the plates (1, 2, 3, 4), (5, 6, 7, 8), (9, 10, 11, 12), (13, +14, 15, 16) in successive rows from the top to the bottom. Then +transfer the apple from 8 to 10 and play as follows, always removing +the apple jumped over: 9-11, 1-9, 13-5, 16-8, 4-12, 12-10, 3-1, 1-9, +9-11.</p> + +<hr style="width: 30%;" /> +<p><a name="X_229_THE_NINE_ALMONDSa" id="X_229_THE_NINE_ALMONDSa"></a><a href="#X_229_THE_NINE_ALMONDS"><b>229.—THE NINE ALMONDS.—<i>solution</i></b></a></p> + +<p>This puzzle may be solved in as few as four moves, in the following +manner: Move 5 over 8, 9, 3, 1. Move 7 over 4. Move 6 over 2 and 7. +Move 5 over 6, and all the counters are removed except 5, which is +left in the central square that it originally occupied.</p> + +<hr style="width: 30%;" /> +<p><a name="X_230_THE_TWELVE_PENNIESa" id="X_230_THE_TWELVE_PENNIESa"></a><a href="#X_230_THE_TWELVE_PENNIES"><b>230.—THE TWELVE PENNIES.—<i>solution</i></b></a></p> + +<p>Here is one of several solutions. Move 12 to 3, 7 to 4, 10 to 6, 8 to +1, 9 to 5, 11 to 2.</p> + +<hr style="width: 30%;" /> +<p><a name="X_231_PLATES_AND_COINSa" id="X_231_PLATES_AND_COINSa"></a><a href="#X_231_PLATES_AND_COINS"><b>231.—PLATES AND COINS.—<i>solution</i></b></a></p> + +<p>Number the plates from 1 to 12 in the order that the boy is seen to be +going in the illustration. Starting from 1, proceed as follows, where +"1 to 4" means that you take the coin from plate No. 1 and transfer it +to plate No. 4: 1 to 4, 5 to 8, 9 to 12, 3 to 6, 7 to 10, 11 to 2, and +complete the last revolution to 1, making three revolutions in all. Or +you can proceed this way: 4 to 7, 8 to 11, 12 to 3, 2 to 5, 6 to 9, 10 +to 1. It is easy to solve in four revolutions, but the solutions in +three are more difficult to discover.</p> + +<p>This is "The Riddle of the Fishpond" (No. 41, <i>Canterbury Puzzles</i>) in +a different dress.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 196<a name="Page_196" id="Page_196"></a></span><a name="X_232_CATCHING_THE_MICEa" id="X_232_CATCHING_THE_MICEa"></a><a href="#X_232_CATCHING_THE_MICE"><b>232.—CATCHING THE MICE.—<i>solution</i></b></a></p> + +<p>In order that the cat should eat every thirteenth mouse, and the white +mouse last of all, it is necessary that the count should begin at the +seventh mouse (calling the white one the first)—that is, at the one +nearest the tip of the cat's tail. In this case it is not at all +necessary to try starting at all the mice in turn until you come to +the right one, for you can just start anywhere and note how far +distant the last one eaten is from the starting point. You will find +it to be the eighth, and therefore must start at the eighth, counting +backwards from the white mouse. This is the one I have indicated.</p> + +<p>In the case of the second puzzle, where you have to find the smallest +number with which the cat may start at the white mouse and eat this +one last of all, unless you have mastered the general solution of the +problem, which is very difficult, there is no better course open to +you than to try every number in succession until you come to one that +works correctly. The smallest number is twenty-one. If you have to +proceed by trial, you will shorten your labour a great deal by only +counting out the remainders when the number is divided successively by +13, 12, 11, 10, etc. Thus, in the case of 21, we have the remainders +8, 9, 10, 1, 3, 5, 7, 3, 1, 1, 3, 1, 1. Note that I do not give the +remainders of 7, 3, and 1 as nought, but as 7, 3, and 1. Now, count +round each of these numbers in turn, and you will find that the white +mouse is killed last of all. Of course, if we wanted simply any +number, not the smallest, the solution is very easy, for we merely +take the least common multiple of 13, 12, 11, 10, etc. down to 2. This +is 360360, and you will find that the first count kills the thirteenth +mouse, the next the twelfth, the next the eleventh, and so on down to +the first. But the most arithmetically inclined cat could not be +expected to take such a big number when a small one like twenty-one +would equally serve its purpose.</p> + +<p>In the third case, the smallest number is 100. The number 1,000 would +also do, and there are just seventy-two other numbers between these +that the cat might employ with equal success.</p> + +<hr style="width: 30%;" /> +<p><a name="X_233_THE_ECCENTRIC_CHEESEMONGERa" id="X_233_THE_ECCENTRIC_CHEESEMONGERa"></a><a href="#X_233_THE_ECCENTRIC_CHEESEMONGER"><b>233.—THE ECCENTRIC CHEESEMONGER.—<i>solution</i></b></a></p> + +<p>To leave the three piles at the extreme ends of the rows, the cheeses +may be moved as follows—the numbers refer to the cheeses and not to +their positions in the row: 7-2, 8-7, 9-8, 10-15, 6-10, 5-6, 14-16, +13-14, 12-13, 3-1, 4-3, 11-4. This is probably the easiest solution of +all to find. To get three of the piles on cheeses 13, 14, and 15, play +thus: 9-4, 10-9, 11-10, 6-14, 5-6, 12-15, 8-12, 7-8, 16-5, 3-13, 2-3, +1-2. To leave the piles on cheeses 3, 5, 12, and 14, play thus: 8-3, +9-14, 16-12, 1-5, 10-9, 7-10, 11-8, 2-1, 4-16, 13-2, 6-11, 15-4.</p> + +<hr style="width: 30%;" /> +<p><a name="X_234_THE_EXCHANGE_PUZZLEa" id="X_234_THE_EXCHANGE_PUZZLEa"></a><a href="#X_234_THE_EXCHANGE_PUZZLE"><b>234.—THE EXCHANGE PUZZLE.—<i>solution</i></b></a></p> + +<p>Make the following exchanges of pairs: H-K, H-E, H-C, H-A, I-L, I-F, +I-D, K-L, G-J, J-A, F-K, L-E, D-K, E-F, E-D, E-B, B-K. It will be +found that, although the white counters can be moved to their proper +places in 11 moves, if we omit all consideration of exchanges, yet the +black cannot be so moved in fewer than 17 moves. So we have to +introduce waste moves with the white counters to equal the minimum +required by the black. Thus fewer than 17 moves must be impossible. +Some of the moves are, of course, interchangeable.</p> + +<hr style="width: 30%;" /> +<p><a name="X_235_TORPEDO_PRACTICEa" id="X_235_TORPEDO_PRACTICEa"></a><a href="#X_235_TORPEDO_PRACTICE"><b>235.—TORPEDO PRACTICE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a235.png" width="400" height="398" alt="" title="" /> +</div> + +<p>If the enemy's fleet be anchored in the formation shown in the +illustration, it will be seen that as many as ten out of the sixteen +ships may be blown up by discharging the torpedoes in the order +indicated by the numbers and in the directions indicated by the +arrows. As each torpedo in succession passes under three ships and +sinks the fourth, strike out each vessel with the pencil as it is +sunk.</p> + +<hr style="width: 30%;" /> +<p><a name="X_236_THE_HAT_PUZZLEa" id="X_236_THE_HAT_PUZZLEa"></a><a href="#X_236_THE_HAT_PUZZLE"><b>236.—THE HAT PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a236.png" width="400" height="216" alt="" title="" /> +</div> + +<p>I suggested that the reader should try this puzzle with counters, so I +give my solution in that form. The silk hats are represented by black +counters and the felt hats by white counters. The first row shows the +hats in their original positions, and then each succes<span class='pagenum'>Pg 197<a name="Page_197" id="Page_197"></a></span>sive row shows +how they appear after one of the five manipulations. It will thus be +seen that we first move hats 2 and 3, then 7 and 8, then 4 and 5, then +10 and 11, and, finally, 1 and 2, leaving the four silk hats together, +the four felt hats together, and the two vacant pegs at one end of the +row. The first three pairs moved are dissimilar hats, the last two +pairs being similar. There are other ways of solving the puzzle.</p> + +<hr style="width: 30%;" /> +<p><a name="X_237_BOYS_AND_GIRLSa" id="X_237_BOYS_AND_GIRLSa"></a><a href="#X_237_BOYS_AND_GIRLS"><b>237.—BOYS AND GIRLS.—<i>solution</i></b></a></p> + +<p>There are a good many different solutions to this puzzle. Any +contiguous pair, except 7-8, may be moved first, and after the first +move there are variations. The following solution shows the position +from the start right through each successive move to the end:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>.</td><td align='center'>.</td><td align='center'>1</td><td align='center'>2</td><td align='center'>3</td><td align='center'>4</td><td align='center'>5</td><td align='center'>6</td><td align='center'>7</td><td align='center'>8</td></tr> +<tr><td align='center'>4</td><td align='center'>3</td><td align='center'>1</td><td align='center'>2</td><td align='center'>.</td><td align='center'>.</td><td align='center'>5</td><td align='center'>6</td><td align='center'>7</td><td align='center'>8</td></tr> +<tr><td align='center'>4</td><td align='center'>3</td><td align='center'>1</td><td align='center'>2</td><td align='center'>7</td><td align='center'>6</td><td align='center'>5</td><td align='center'>.</td><td align='center'>.</td><td align='center'>8</td></tr> +<tr><td align='center'>4</td><td align='center'>3</td><td align='center'>1</td><td align='center'>2</td><td align='center'>7</td><td align='center'>.</td><td align='center'>.</td><td align='center'>5</td><td align='center'>6</td><td align='center'>8</td></tr> +<tr><td align='center'>4</td><td align='center'>.</td><td align='center'>.</td><td align='center'>2</td><td align='center'>7</td><td align='center'>1</td><td align='center'>3</td><td align='center'>5</td><td align='center'>6</td><td align='center'>8</td></tr> +<tr><td align='center'>4</td><td align='center'>8</td><td align='center'>6</td><td align='center'>2</td><td align='center'>7</td><td align='center'>1</td><td align='center'>3</td><td align='center'>5</td><td align='center'>.</td><td align='center'>.</td></tr> +</table></div> + +<hr style="width: 30%;" /> +<p><a name="X_238_ARRANGING_THE_JAMPOTSa" id="X_238_ARRANGING_THE_JAMPOTSa"></a><a href="#X_238_ARRANGING_THE_JAMPOTS"><b>238.—ARRANGING THE JAMPOTS.—<i>solution</i></b></a></p> + +<p>Two of the pots, 13 and 19, were in their proper places. As every +interchange may result in a pot being put in its place, it is clear +that twenty-two interchanges will get them all in order. But this +number of moves is not the fewest possible, the correct answer being +seventeen. Exchange the following pairs: (3-1, 2-3), (15-4, 16-15), +(17-7, 20-17), (24-10, 11-24, 12-11), (8-5, 6-8, 21-6, 23-21, 22-23, +14-22, 9-14, 18-9). When you have made the interchanges within any +pair of brackets, all numbers within those brackets are in their +places. There are five pairs of brackets, and 5 from 22 gives the +number of changes required—17.</p> + +<hr style="width: 30%;" /> +<p><a name="X_239_A_JUVENILE_PUZZLEa" id="X_239_A_JUVENILE_PUZZLEa"></a><a href="#X_239_A_JUVENILE_PUZZLE"><b>239.—A JUVENILE PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a239.png" width="400" height="230" alt="" title="" /> +</div> + +<p>As the conditions are generally understood, this puzzle is incapable +of solution. This can be demonstrated quite easily. So we have to look +for some catch or quibble in the statement of what we are asked to do. +Now if you fold the paper and then push the point of your pencil down +between the fold, you can with one stroke make the two lines CD and EF +in our diagram. Then start at A, and describe the line ending at B. +Finally put in the last line GH, and the thing is done strictly within +the conditions, since folding the paper is not actually forbidden. Of +course the lines are here left unjoined for the purpose of clearness.</p> + +<p>In the rubbing out form of the puzzle, first rub out A to B with a +single finger in one stroke. Then rub out the line GH with one finger. +Finally, rub out the remaining two vertical lines with two fingers at +once! That is the old trick.</p> + +<hr style="width: 30%;" /> +<p><a name="X_240_THE_UNION_JACKa" id="X_240_THE_UNION_JACKa"></a><a href="#X_240_THE_UNION_JACK"><b>240.—THE UNION JACK.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a240.png" width="400" height="288" alt="" title="" /> +</div> + +<p>There are just sixteen points (all on the outside) where three roads +may be said to join. These are called by mathematicians "odd nodes." +There is a rule that tells us that in the case of a drawing like the +present one, where there are sixteen odd nodes, it requires eight +separate strokes or routes (that is, half as many as there are odd +nodes) to complete it. As we have to produce as much as possible with +only one of these eight strokes, it is clearly necessary to contrive +that the seven strokes from odd node to odd node shall be as short as +possible. Start at A and end at B, or go the reverse way.</p> + +<hr style="width: 30%;" /> +<p><a name="X_241_THE_DISSECTED_CIRCLEa" id="X_241_THE_DISSECTED_CIRCLEa"></a><a href="#X_241_THE_DISSECTED_CIRCLE"><b>241.—THE DISSECTED CIRCLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a241.png" width="400" height="388" alt="" title="" /> +</div> + +<p>It can be done in twelve continuous strokes, thus: Start at A in the +illustration, and eight <span class='pagenum'>Pg 198<a name="Page_198" id="Page_198"></a></span>strokes, forming the star, will bring you +back to A; then one stroke round the circle to B, one stroke to C, one +round the circle to D, and one final stroke to E—twelve in all. Of +course, in practice the second circular stroke will be over the first +one; it is separated in the diagram, and the points of the star not +joined to the circle, to make the solution clear to the eye.</p> +<hr style="width: 30%;" /> +<p><a name="X_242_THE_TUBE_INSPECTORS_PUZZLEa" id="X_242_THE_TUBE_INSPECTORS_PUZZLEa"></a><a href="#X_242_THE_TUBE_INSPECTORS_PUZZLE"><b>242.—THE TUBE INSPECTOR'S PUZZLE.—<i>solution</i></b></a></p> + +<p>The inspector need only travel nineteen miles if he starts at B and +takes the following route: B A D G D E F I F C B E H K L I H G J K. Thus the only +portions of line travelled over twice are the two sections D to G and +F to I. Of course, the route may be varied, but it cannot be +shortened.</p> +<hr style="width: 30%;" /> +<p><a name="X_243_VISITING_THE_TOWNSa" id="X_243_VISITING_THE_TOWNSa"></a><a href="#X_243_VISITING_THE_TOWNS"><b>243.—VISITING THE TOWNS.—<i>solution</i></b></a></p> + +<p>Note that there are six towns, from which only two roads issue. Thus 1 +must lie between 9 and 12 in the circular route. Mark these two roads +as settled. Similarly mark 9, 5, 14, and 4, 8, 14, and 10, 6, 15, and +10, 2, 13, and 3, 7, 13. All these roads must be taken. Then you will +find that he must go from 4 to 15, as 13 is closed, and that he is +compelled to take 3, 11, 16, and also 16, 12. Thus, there is only one +route, as follows: 1, 9, 5, 14, 8, 4, 15, 6, 10, 2, 13, 7, 3, 11, 16, +12, 1, or its reverse—reading the line the other way. Seven roads are +not used.</p> +<hr style="width: 30%;" /> +<p><a name="X_244_THE_FIFTEEN_TURNINGSa" id="X_244_THE_FIFTEEN_TURNINGSa"></a><a href="#X_244_THE_FIFTEEN_TURNINGS"><b>244.—THE FIFTEEN TURNINGS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a244.png" width="400" height="398" alt="" title="" /> +</div> + +<p>It will be seen from the illustration (where the roads not used are +omitted) that the traveller can go as far as seventy miles in fifteen +turnings. The turnings are all numbered in the order in which they are +taken. It will be seen that he never visits nineteen of the towns. He +might visit them all in fifteen turnings, never entering any town +twice, and end at the black town from which he starts (see "The Rook's +Tour," No. 320), but such a tour would only take him sixty-four miles.</p> +<hr style="width: 30%;" /> +<p><a name="X_245_THE_FLY_ON_THE_OCTAHEDRONa" id="X_245_THE_FLY_ON_THE_OCTAHEDRONa"></a><a href="#X_245_THE_FLY_ON_THE_OCTAHEDRON"><b>245.—THE FLY ON THE OCTAHEDRON.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a245.png" width="400" height="350" alt="" title="" /> +</div> + +<p>Though we cannot really see all the sides of the octahedron at once, +we can make a projection of it that suits our purpose just as well. In +the diagram the six points represent the six angles of the octahedron, +and four lines proceed from every point under exactly the same +conditions as the twelve edges of the solid. Therefore if we start at +the point A and go over all the lines once, we must always end our +route at A. And the number of different routes is just 1,488, counting +the reverse way of any route as different. It would take too much +space to show how I make the count. It can be done in about five +minutes, but an explanation of the method is difficult. The reader is +therefore asked to accept my answer as correct.</p> +<hr style="width: 30%;" /> +<p><a name="X_246_THE_ICOSAHEDRON_PUZZLEa" id="X_246_THE_ICOSAHEDRON_PUZZLEa"></a><a href="#X_246_THE_ICOSAHEDRON_PUZZLE"><b>246.—THE ICOSAHEDRON PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a246.png" width="400" height="340" alt="" title="" /> +</div> + +<p>There are thirty edges, of which eighteen were visible in the original +illustration, represented <span class='pagenum'>Pg 199<a name="Page_199" id="Page_199"></a></span>in the following diagram by the hexagon +NAESGD. By this projection of the solid we get an imaginary view of +the remaining twelve edges, and are able to see at once their +direction and the twelve points at which all the edges meet. The +difference in the length of the lines is of no importance; all we want +is to present their direction in a graphic manner. But in case the +novice should be puzzled at only finding nineteen triangles instead of +the required twenty, I will point out that the apparently missing +triangle is the outline HIK.</p> + +<p>In this case there are twelve odd nodes; therefore six distinct and +disconnected routes will be needful if we are not to go over any lines +twice. Let us therefore find the greatest distance that we may so +travel in one route.</p> + +<p>It will be noticed that I have struck out with little cross strokes +five lines or edges in the diagram. These five lines may be struck out +anywhere so long as they do not join one another, and so long as one +of them does not connect with N, the North Pole, from which we are to +start. It will be seen that the result of striking out these five +lines is that all the nodes are now even except N and S. Consequently +if we begin at N and stop at S we may go over all the lines, except +the five crossed out, without traversing any line twice. There are +many ways of doing this. Here is one route: N to H, I, K, S, I, E, S, +G, K, D, H, A, N, B, A, E, F, B, C, G, D, N, C, F, S. By thus making +five of the routes as short as is possible—simply from one node to +the next—we are able to get the greatest possible length for our +sixth line. A greater distance in one route, without going over the +same ground twice, it is not possible to get.</p> + +<p>It is now readily seen that those five erased lines must be gone over +twice, and they may be "picked up," so to speak, at any points of our +route. Thus, whenever the traveller happens to be at I he can run up +to A and back before proceeding on his route, or he may wait until he +is at A and then run down to I and back to A. And so with the other +lines that have to be traced twice. It is, therefore, clear that he +can go over 25 of the lines once only (25 × 10,000 miles = 250,000 +miles) and 5 of the lines twice (5 × 20,000 miles = 100,000 miles), the +total, 350,000 miles, being the length of his travels and the shortest +distance that is possible in visiting the whole body.</p> + +<p>It will be noticed that I have made him end his travels at S, the +South Pole, but this is not imperative. I might have made him finish +at any of the other nodes, except the one from which he started. +Suppose it had been required to bring him home again to N at the end +of his travels. Then instead of suppressing the line AI we might leave +that open and close IS. This would enable him to complete his 350,000 +miles tour at A, and another 10,000 miles would take him to his own +fireside. There are a great many different routes, but as the lengths +of the edges are all alike, one course is as good as another. To make +the complete 350,000 miles tour from N to S absolutely clear to +everybody, I will give it entire: N to H, I, A, I, K, H, K, S, I, E, +S, G, F, G, K, D, C, D, H, A, N, B, E, B, A, E, F, B, C, G, D, N, C, +F, S—that is, thirty-five lines of 10,000 miles each.</p> + +<hr style="width: 30%;" /> +<p><a name="X_247_INSPECTING_A_MINEa" id="X_247_INSPECTING_A_MINEa"></a><a href="#X_247_INSPECTING_A_MINE"><b>247.—INSPECTING A MINE.—<i>solution</i></b></a></p> + +<p>Starting from A, the inspector need only travel 36 furlongs if he +takes the following route: A to B, G, H, C, D, I, H, M, N, I, J, O, N, +S, R, M, L, G, F, K, L, Q, R, S, T, O, J, E, D, C, B, A, F, K, P, Q. +He thus passes between A and B twice, between C and D twice, between F +and K twice, between J and O twice, and between R and S twice—five +repetitions. Therefore 31 passages plus 5 repeated equal 36 furlongs. +The little pitfall in this puzzle lies in the fact that we start from +an even node. Otherwise we need only travel 35 furlongs.</p> + +<hr style="width: 30%;" /> +<p><a name="X_248_THE_CYCLISTS_TOURa" id="X_248_THE_CYCLISTS_TOURa"></a><a href="#X_248_THE_CYCLISTS_TOUR"><b>248.—THE CYCLIST'S TOUR.—<i>solution</i></b></a></p> + +<p>When Mr. Maggs replied, "No way, I'm sure," he was not saying that the +thing was impossible, but was really giving the actual route by which +the problem can be solved. Starting from the star, if you visit the +towns in the order, NO WAY, I'M SURE, you will visit every town once, +and only once, and end at E. So both men were correct. This was the +little joke of the puzzle, which is not by any means difficult.</p> + +<hr style="width: 30%;" /> +<p><a name="X_249_THE_SAILORS_PUZZLEa" id="X_249_THE_SAILORS_PUZZLEa"></a><a href="#X_249_THE_SAILORS_PUZZLE"><b>249.—THE SAILOR'S PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a249.png" width="400" height="505" alt="" title="" /> +</div> + +<p>There are only four different routes (or eight, if we count the +reverse ways) by which the sailor can start at the island marked A, +visit all the islands once, and once only, and return again to A. Here +they are:—</p> + +<p><span class='pagenum'>Pg 200<a name="Page_200" id="Page_200"></a></span>A I P T L O E H R Q D C F U G N S K M B A A I P T S N G L O E U F C D +K M B Q R H A A B M K S N G L T P I O E U F C D Q R H A A I P T L O E +U G N S K M B Q D C F R H A</p> + +<p>Now, if the sailor takes the first route he will make C his 12th +island (counting A as 1); by the second route he will make C his 13th +island; by the third route, his 16th island; and by the fourth route, +his 17th island. If he goes the reverse way, C will be respectively +his 10th, 9th, 6th, and 5th island. As these are the only possible +routes, it is evident that if the sailor puts off his visit to C as +long as possible, he must take the last route reading from left to +right. This route I show by the dark lines in the diagram, and it is +the correct answer to the puzzle.</p> + +<p>The map may be greatly simplified by the "buttons and string" method, +explained in the solution to <a href="#X_341_THE_FOUR_FROGSa">No. 341</a>, "The Four Frogs."</p> + +<hr style="width: 30%;" /> +<p><a name="X_250_THE_GRAND_TOURa" id="X_250_THE_GRAND_TOURa"></a><a href="#X_250_THE_GRAND_TOUR"><b>250.—THE GRAND TOUR.—<i>solution</i></b></a></p> + +<p>The first thing to do in trying to solve a puzzle like this is to +attempt to simplify it. If you look at Fig. 1, you will see that it is +a simplified version of the map. Imagine the circular towns to be +buttons and the railways to be connecting strings. (See solution to +<a href="#X_341_THE_FOUR_FROGSa">No. 341.</a>) Then, it will be seen, we have simply "straightened out" the +previous diagram without affecting the conditions. Now we can further +simplify by converting Fig. 1 into Fig. 2, which is a portion of a +chessboard. Here the directions of the railways will resemble the +moves of a rook in chess—that is, we may move in any direction +parallel to the sides of the diagram, but not diagonally. Therefore +the first town (or square) visited must be a black one; the second +must be a white; the third must be a black; and so on. Every odd +square visited will thus be black and every even one white. Now, we +have 23 squares to visit (an odd number), so the last square visited +must be black. But Z happens to be white, so the puzzle would seem to +be impossible of solution.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a250.png" width="600" height="414" alt="" title="" /> +</div> + +<p>As we were told that the man "succeeded" in carrying put his plan, we +must try to find some loophole in the conditions. He was to "enter +every town once and only once," and we find no prohibition against his +entering once the town A after leaving it, especially as he has never +left it since he was born, and would thus be "entering" it for the +first time in his life. But he must return at once from the first town +he visits, and then he will have only 22 towns to visit, and as 22 is +an even number, there is no reason why he should not end on the white +square Z. A possible route for him is indicated by the dotted line +from A to Z. This route is repeated by the dark lines in Fig. 1, and +the reader will now have no difficulty in applying; it to the original +map. We have thus proved that the puzzle can only be solved by a +return to A immediately after leaving it.</p> +<hr style="width: 30%;" /> +<p><a name="X_251_WATER_GAS_AND_ELECTRICITYa" id="X_251_WATER_GAS_AND_ELECTRICITYa"></a><a href="#X_251_WATER_GAS_AND_ELECTRICITY"><b>251.—WATER, GAS, AND ELECTRICITY.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a251.png" width="400" height="303" alt="" title="" /> +</div> + +<p>According to the conditions, in the strict sense in which one at first +understands them, there<span class='pagenum'>Pg 201<a name="Page_201" id="Page_201"></a></span>is no possible solution to this puzzle. In such a dilemma one always +has to look for some verbal quibble or trick. If the owner of house A +will allow the water company to run their pipe for house C through his +property (and we are not bound to assume that he would object), then +the difficulty is got over, as shown in our illustration. It will be +seen that the dotted line from W to C passes through house A, but no +pipe ever crosses another pipe.</p> + +<hr style="width: 30%;" /> +<p><a name="X_252_A_PUZZLE_FOR_MOTORISTSa" id="X_252_A_PUZZLE_FOR_MOTORISTSa"></a><a href="#X_252_A_PUZZLE_FOR_MOTORISTS"><b>252.—A PUZZLE FOR MOTORISTS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/a252.png" width="500" height="307" alt="" title="" /> +</div> + +<p>The routes taken by the eight drivers are shown in the illustration, +where the dotted line roads are omitted to make the paths clearer to +the eye.</p> + +<hr style="width: 30%;" /> +<p><a name="X_253_A_BANK_HOLIDAY_PUZZLEa" id="X_253_A_BANK_HOLIDAY_PUZZLEa"></a><a href="#X_253_A_BANK_HOLIDAY_PUZZLE"><b>253.—A BANK HOLIDAY PUZZLE.—<i>solution</i></b></a></p> + +<p>The simplest way is to write in the number of routes to all the towns +in this manner. Put a 1 on all the towns in the top row and in the +first column. Then the number of routes to any town will be the sum of +the routes to the town immediately above and to the town immediately +to the left. Thus the routes in the second row will be 1, 2, 3, 4, 5, +6, etc., in the third row, 1, 3, 6, 10, 15, 21, etc.; and so on with +the other rows. It will then be seen that the only town to which there +are exactly 1,365 different routes is the twelfth town in the fifth +row—the one immediately over the letter E. This town was therefore +the cyclist's destination.</p> + +<p>The general formula for the number of routes from one corner to the +corner diagonally opposite on any such rectangular reticulated +arrangement, under the conditions as to direction, is <sup>(<i>m</i> + <i>n</i>)!</sup>/<sub><i>m</i>!<i>n</i>!</sub>, +where m is the number of towns on one side, less one, and n the number +on the other side, less one. Our solution involves the case where +there are 12 towns by 5. Therefore <i>m</i> = 11 and <i>n</i> = 4. Then the formula +gives us the answer 1,365 as above.</p> + +<hr style="width: 30%;" /> +<p><a name="X_254_THE_MOTOR-CAR_TOURa" id="X_254_THE_MOTOR-CAR_TOURa"></a><a href="#X_254_THE_MOTOR-CAR_TOUR"><b>254.—THE MOTOR-CAR TOUR.—<i>solution</i></b></a></p> + +<p>First of all I will ask the reader to compare the original square +diagram with the circular one shown in Figs. 1, 2, and 3 below. If for +the moment we ignore the shading (the purpose of which I shall proceed +to explain), we find that the circular diagram in each case is merely +a simplification of the original square one—that is, the roads from A +lead to B, E, and M in both cases, the roads from L (London) lead to +I, K, and S, and so on. The form below, being circular and +symmetrical, answers my purpose better in applying a mechanical +solution, and I therefore adopt it without altering in any way the +conditions of the puzzle. If such a question as distances from town to +town came into the problem, the new diagrams might require the +addition of numbers to indicate these distances, or they might +conceivably not be at all practicable.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a254.png" width="600" height="221" alt="" title="" /> +</div> + +<p>Now, I draw the three circular diagrams, as shown, on a sheet of paper +and then cut out three pieces of cardboard of the forms indicated by +the shaded parts of these diagrams. It can be shown that every route, +if marked out with a red pencil, will form one or other of the designs +indicated by the edges of the cards, or a reflection thereof. Let us +direct our attention to Fig. 1. Here the card is so placed that the +star is at the town T; it therefore gives us (by following the edge of +the card) one of the circular routes from London: L, S, R, T, M, A, E, +P, O, J, D, C, B, G, N, Q, K, H, F, I, L. If we went the other way, we +should get L, I, F, H, K, Q, etc., but these reverse routes were not +to be counted. When we have written out this first route we revolve +the card until the <span class='pagenum'>Pg 202<a name="Page_202" id="Page_202"></a></span>star is at M, when we get another different route, +at A a third route, at E a fourth route, and at P a fifth route. We +have thus obtained five different routes by revolving the card as it +lies. But it is evident that if we now take up the card and replace it +with the other side uppermost, we shall in the same manner get five +other routes by revolution.</p> + +<p>We therefore see how, by using the revolving card in Fig. 1, we may, +without any difficulty, at once write out ten routes. And if we employ +the cards in Figs. 2 and 3, we similarly obtain in each case ten other +routes. These thirty routes are all that are possible. I do not give +the actual proof that the three cards exhaust all the possible cases, +but leave the reader to reason that out for himself. If he works out +any route at haphazard, he will certainly find that it falls into one +or other of the three categories.</p> + +<hr style="width: 30%;" /> +<p><a name="X_255_THE_LEVEL_PUZZLEa" id="X_255_THE_LEVEL_PUZZLEa"></a><a href="#X_255_THE_LEVEL_PUZZLE"><b>255.—THE LEVEL PUZZLE.—<i>solution</i></b></a></p> + +<p>Let us confine our attention to the L in the top left-hand corner. +Suppose we go by way of the E on the right: we must then go straight +on to the V, from which letter the word may be completed in four ways, +for there are four E's available through which we may reach an L. +There are therefore four ways of reading through the right-hand E. It +is also clear that there must be the same number of ways through the E +that is immediately below our starting point. That makes eight. If, +however, we take the third route through the E on the diagonal, we +then have the option of any one of the three V's, by means of each of +which we may complete the word in four ways. We can therefore spell +LEVEL in twelve ways through the diagonal E. Twelve added to eight +gives twenty readings, all emanating from the L in the top left-hand +corner; and as the four corners are equal, the answer must be four +times twenty, or eighty different ways.</p> + +<hr style="width: 30%;" /> +<p><a name="X_256_THE_DIAMOND_PUZZLEa" id="X_256_THE_DIAMOND_PUZZLEa"></a><a href="#X_256_THE_DIAMOND_PUZZLE"><b>256.—THE DIAMOND PUZZLE.—<i>solution</i></b></a></p> + +<p>There are 252 different ways. The general formula is that, for words +of <i>n</i> letters (not palindromes, as in the case of the next puzzle), +when grouped in this manner, there are always 2<sup>(n+1)</sup> - 4 different +readings. This does not allow diagonal readings, such as you would get +if you used instead such a word as DIGGING, where it would be possible +to pass from one G to another G by a diagonal step.</p> + +<hr style="width: 30%;" /> +<p><a name="X_257_THE_DEIFIED_PUZZLEa" id="X_257_THE_DEIFIED_PUZZLEa"></a><a href="#X_257_THE_DEIFIED_PUZZLE"><b>257.—THE DEIFIED PUZZLE.—<i>solution</i></b></a></p> + +<p>The correct answer is 1,992 different ways. Every F is either a corner +F or a side F—standing next to a corner in its own square of F's. +Now, FIED may be read <i>from</i> a corner F in 16 ways; therefore DEIF may +be read <i>into</i> a corner F also in 16 ways; hence DEIFIED may be read +<i>through</i> a corner F in 16 × 16 = 256 ways. Consequently, the four +corner F's give 4 × 256 = 1,024 ways. Then FIED may be read from a +side F in 11 ways, and DEIFIED therefore in 121 ways. But there are +eight side F's; consequently these give together 8 × 121 = 968 ways. +Add 968 to 1,024 and we get the answer, 1,992.</p> + +<p>In this form the solution will depend on whether the number of letters +in the palindrome be odd or even. For example, if you apply the word +NUN in precisely the same manner, you will get 64 different readings; +but if you use the word NOON, you will only get 56, because you cannot +use the same letter twice in immediate succession (since you must +"always pass from one letter to another") or diagonal readings, and +every reading must involve the use of the central N.</p> + +<p>The reader may like to find for himself the general formula in this +case, which is complex and difficult. I will merely add that for such +a case as MADAM, dealt with in the same way as DEIFIED, the number of +readings is 400.</p> + +<hr style="width: 30%;" /> +<p><a name="X_258_THE_VOTERS_PUZZLEa" id="X_258_THE_VOTERS_PUZZLEa"></a><a href="#X_258_THE_VOTERS_PUZZLE"><b>258.—THE VOTERS' PUZZLE.—<i>solution</i></b></a></p> + +<p>THE number of readings here is 63,504, as in the case of "WAS IT A RAT +I SAW" (No. 30, <i>Canterbury Puzzles</i>). The general formula is that for +palindromic sentences containing 2<i>n</i> + 1 letters there are [4(2<sup><i>n</i></sup> - +1)]² readings.</p> + +<hr style="width: 30%;" /> +<p><a name="X_259_HANNAHS_PUZZLEa" id="X_259_HANNAHS_PUZZLEa"></a><a href="#X_259_HANNAHS_PUZZLE"><b>259.—HANNAH'S PUZZLE.—<i>solution</i></b></a></p> + +<p>Starting from any one of the N's, there are 17 different readings of +NAH, or 68 (4 times 17) for the 4 N's. Therefore there are also 68 +ways of spelling HAN. If we were allowed to use the same N twice in a +spelling, the answer would be 68 times 68, or 4,624 ways. But the +conditions were, "always passing from one letter to another." +Therefore, for every one of the 17 ways of spelling HAN with a +particular N, there would be 51 ways (3 times 17) of completing the +NAH, or 867 (17 times 51) ways for the complete word. Hence, as there +are four N's to use in HAN, the correct solution of the puzzle is +3,468 (4 times 867) different ways.</p> + +<hr style="width: 30%;" /> +<p><a name="X_260_THE_HONEYCOMB_PUZZLEa" id="X_260_THE_HONEYCOMB_PUZZLEa"></a><a href="#X_260_THE_HONEYCOMB_PUZZLE"><b>260.—THE HONEYCOMB PUZZLE.—<i>solution</i></b></a></p> + +<p>The required proverb is, "There is many a slip 'twixt the cup and the +lip." Start at the T on the outside at the bottom right-hand corner, +pass to the H above it, and the rest is easy.</p> + +<hr style="width: 30%;" /> +<p><a name="X_261_THE_MONK_AND_THE_BRIDGESa" id="X_261_THE_MONK_AND_THE_BRIDGESa"></a><a href="#X_261_THE_MONK_AND_THE_BRIDGES"><b>261.—THE MONK AND THE BRIDGES.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/a261.png" width="300" height="425" alt="" title="" /> +</div> + +<p>The problem of the Bridges may be reduced to the simple diagram shown +in illustration. The <span class='pagenum'>Pg 203<a name="Page_203" id="Page_203"></a></span>point M represents the Monk, the point I the +Island, and the point Y the Monastery. Now the only direct ways from M +to I are by the bridges <i>a</i> and <i>b</i>; the only direct ways from I to Y +are by the bridges <i>c</i> and <i>d</i>; and there is a direct way from M to Y +by the bridge <i>e</i>. Now, what we have to do is to count all the routes +that will lead from M to Y, passing over all the bridges, <i>a</i>, <i>b</i>, +<i>c</i>, <i>d</i>, and <i>e</i> once and once only. With the simple diagram under +the eye it is quite easy, without any elaborate rule, to count these +routes methodically. Thus, starting from <i>a</i>, <i>b</i>, we find there are +only two ways of completing the route; with <i>a, c</i>, there are only two +routes; with <i>a</i>, <i>d</i>, only two routes; and so on. It will be found +that there are sixteen such routes in all, as in the following list:—</p> + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="0" summary=""> +<tr><td align='center'><i>a b e c d</i></td></tr> +<tr><td align='center'><i>a b e d c</i></td></tr> +<tr><td align='center'><i>a c d b e</i></td></tr> +<tr><td align='center'><i>a c e b d</i></td></tr> +<tr><td align='center'><i>a d e b c</i></td></tr> +<tr><td align='center'><i>a d c b e</i></td></tr> +<tr><td align='center'><i>b a e c d</i></td></tr> +<tr><td align='center'><i>b a e d c</i></td></tr> +<tr><td align='center'><i>b c d a e</i></td></tr> +<tr><td align='center'><i>b c e a d</i></td></tr> +<tr><td align='center'><i>b d c a e</i></td></tr> +<tr><td align='center'><i>b d e a c</i></td></tr> +<tr><td align='center'><i>e c a b d</i></td></tr> +<tr><td align='center'><i>e c b a d</i></td></tr> +<tr><td align='center'><i>e d a b c</i></td></tr> +<tr><td align='center'><i>e d b a c</i></td></tr> +</table></div> + +<p>If the reader will transfer the letters indicating the bridges from +the diagram to the corresponding bridges in the original illustration, +everything will be quite obvious.</p> + +<hr style="width: 30%;" /> +<p><a name="X_262_THOSE_FIFTEEN_SHEEPa" id="X_262_THOSE_FIFTEEN_SHEEPa"></a><a href="#X_262_THOSE_FIFTEEN_SHEEP"><b>262.—THOSE FIFTEEN SHEEP.—<i>solution</i></b></a></p> + +<p>If we read the exact words of the writer in the cyclopædia, we find +that we are not told that the pens were all necessarily empty! In +fact, if the reader will refer back to the illustration, he will see +that one sheep is already in one of the pens. It was just at this +point that the wily farmer said to me, "<i>Now</i> I'm going to start +placing the fifteen sheep." He thereupon proceeded to drive three from +his flock into the already occupied pen, and then placed four sheep in +each of the other three pens. "There," says he, "you have seen me +place fifteen sheep in four pens so that there shall be the same +number of sheep in every pen." I was, of course, forced to admit that +he was perfectly correct, according to the exact wording of the +question.</p> + +<hr style="width: 30%;" /> +<p><a name="X_263_KING_ARTHURS_KNIGHTSa" id="X_263_KING_ARTHURS_KNIGHTSa"></a><a href="#X_263_KING_ARTHURS_KNIGHTS"><b>263.—KING ARTHUR'S KNIGHTS.—<i>solution</i></b></a></p> + +<p>On the second evening King Arthur arranged the knights and himself in +the following order round the table: A, F, B, D, G, E, C. On the third +evening they sat thus, A, E, B, G, C, F, D. He thus had B next but one +to him on both occasions (the nearest possible), and G was the third +from him at both sittings (the furthest position possible). No other +way of sitting the knights would have been so satisfactory.</p> + +<hr style="width: 30%;" /> +<p><a name="X_264_THE_CITY_LUNCHEONSa" id="X_264_THE_CITY_LUNCHEONSa"></a><a href="#X_264_THE_CITY_LUNCHEONS"><b>264.—THE CITY LUNCHEONS.—<i>solution</i></b></a></p> + +<p>The men may be grouped as follows, where each line represents a day +and each column a table:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>AB</td><td align='center'>CD</td><td align='center'>EF</td><td align='center'>GH</td><td align='center'>IJ</td><td align='center'>KL</td></tr> +<tr><td align='center'>AE</td><td align='center'>DL</td><td align='center'>GK</td><td align='center'>FI</td><td align='center'>CB</td><td align='center'>HJ</td></tr> +<tr><td align='center'>AG</td><td align='center'>LJ</td><td align='center'>FH</td><td align='center'>KC</td><td align='center'>DE</td><td align='center'>IB</td></tr> +<tr><td align='center'>AF</td><td align='center'>JB</td><td align='center'>KI</td><td align='center'>HD</td><td align='center'>LG</td><td align='center'>CE</td></tr> +<tr><td align='center'>AK</td><td align='center'>BE</td><td align='center'>HC</td><td align='center'>IL</td><td align='center'>JF</td><td align='center'>DG</td></tr> +<tr><td align='center'>AH</td><td align='center'>EG</td><td align='center'>ID</td><td align='center'>CJ</td><td align='center'>BK</td><td align='center'>LF</td></tr> +<tr><td align='center'>AI</td><td align='center'>GF</td><td align='center'>CL</td><td align='center'>DB</td><td align='center'>EH</td><td align='center'>JK</td></tr> +<tr><td align='center'>AC</td><td align='center'>FK</td><td align='center'>DJ</td><td align='center'>LE</td><td align='center'>GI</td><td align='center'>BH</td></tr> +<tr><td align='center'>AD</td><td align='center'>KH</td><td align='center'>LB</td><td align='center'>JG</td><td align='center'>FC</td><td align='center'>EI</td></tr> +<tr><td align='center'>AL</td><td align='center'>HI</td><td align='center'>JE</td><td align='center'>BF</td><td align='center'>KD</td><td align='center'>GC</td></tr> +<tr><td align='center'>AJ</td><td align='center'>IC</td><td align='center'>BG</td><td align='center'>EK</td><td align='center'>HL</td><td align='center'>FD</td></tr> +</table></div> + +<p>Note that in every column (except in the case of the A's) all the +letters descend cyclically in the same order, B, E, G, F, up to J, +which is followed by B.</p> + +<hr style="width: 30%;" /> +<p><a name="X_265_A_PUZZLE_FOR_CARD-PLAYERSa" id="X_265_A_PUZZLE_FOR_CARD-PLAYERSa"></a><a href="#X_265_A_PUZZLE_FOR_CARD-PLAYERS"><b>265.—A PUZZLE FOR CARD-PLAYERS.—<i>solution</i></b></a></p> + +<p>In the following solution each of the eleven lines represents a +sitting, each column a table, and each pair of letters a pair of +partners.</p> + +<div class='center'> +<table border="0" cellpadding="6" cellspacing="0" summary=""> +<tr><td align='center'>A B — I L</td><td align='center'>E J — G K</td><td align='center'>F H — C D</td></tr> +<tr><td align='center'>A C — J B</td><td align='center'>F K — H L</td><td align='center'>G I — D E</td></tr> +<tr><td align='center'>A D — K C</td><td align='center'>G L — I B</td><td align='center'>H J — E F</td></tr> +<tr><td align='center'>A E — L D</td><td align='center'>H B — J C</td><td align='center'>I K — F G</td></tr> +<tr><td align='center'>A F — B E</td><td align='center'>I C — K D</td><td align='center'>J L — G H</td></tr> +<tr><td align='center'>A G — C F</td><td align='center'>J D — L E</td><td align='center'>K B — H I</td></tr> +<tr><td align='center'>A H — D G</td><td align='center'>K E — B F</td><td align='center'>L C — I J</td></tr> +<tr><td align='center'>A I — E H</td><td align='center'>L F — C G</td><td align='center'>B D — J K</td></tr> +<tr><td align='center'>A J — F I</td><td align='center'>B G — D H</td><td align='center'>C E — K L</td></tr> +<tr><td align='center'>A K — G J</td><td align='center'>C H — E I</td><td align='center'>D F — L B</td></tr> +<tr><td align='center'>A L — H K</td><td align='center'>D I — F J</td><td align='center'>E G — B C</td></tr> +</table></div> + +<p>It will be seen that the letters B, C, D ...L descend cyclically. The +solution given above is absolutely perfect in all respects. It will be +found that every player has every other player once as his partner and +twice as his opponent.</p> +<hr style="width: 30%;" /> +<p><a name="X_266_A_TENNIS_TOURNAMENTa" id="X_266_A_TENNIS_TOURNAMENTa"></a><a href="#X_266_A_TENNIS_TOURNAMENT"><b>266.—A TENNIS TOURNAMENT.—<i>solution</i></b></a></p> + +<p>Call the men A, B, D, E, and their wives a, b, d, e. Then they may +play as follows without any person ever playing twice with or against +any other person:—</p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'></td><td align='center'>First Court.</td><td align='center'>Second Court.</td></tr> +<tr><td align='center'>1st Day</td><td align='center'>A d against B e</td><td align='center'>D a against E b</td></tr> +<tr><td align='center'>2nd Day</td><td align='center'>A e against D b</td><td align='center'>E a against B d</td></tr> +<tr><td align='center'>3rd Day</td><td align='center'>A b against E d</td><td align='center'>B a against D e</td></tr> +</table></div> + +<p>It will be seen that no man ever plays with or against his own +wife—an ideal arrangement. If the reader wants a hard puzzle, let him +try to arrange eight married couples (in four courts on seven days) +under exactly similar conditions. It can be done, but I leave the +reader in this case the pleasure of seeking the answer and the general +solution.</p> + +<hr style="width: 30%;" /> +<p><a name="X_267_THE_WRONG_HATSa" id="X_267_THE_WRONG_HATSa"></a><a href="#X_267_THE_WRONG_HATS"><b>267.—THE WRONG HATS.—<i>solution</i></b></a></p> + +<p>The number of different ways in which eight persons, with eight hats, +can each take the wrong hat, is 14,833.</p> + +<p>Here are the successive solutions for any number of persons from one +to eight:—</p> + +<p><span class='pagenum'>Pg 204<a name="Page_204" id="Page_204"></a></span></p><p> +<span style="margin-left: 2em;">1 = 0</span><br /> +<span style="margin-left: 2em;">2 = 1</span><br /> +<span style="margin-left: 2em;">3 = 2</span><br /> +<span style="margin-left: 2em;">4 = 9</span><br /> +<span style="margin-left: 2em;">5 = 44</span><br /> +<span style="margin-left: 2em;">6 = 265</span><br /> +<span style="margin-left: 2em;">7 = 1,854</span><br /> +<span style="margin-left: 2em;">8 = 14,833</span><br /> +</p> + +<p>To get these numbers, multiply successively by 2, 3, 4, 5, etc. When +the multiplier is even, add 1; when odd, deduct 1. Thus, 3 × 1 - 1 = 2, +4 × 2 + 1 = 9; 5 × 9 - 1 = 44; and so on. Or you can multiply the sum of the +number of ways for n-1 and n-2 persons by n-1, and so get the solution +for n persons. Thus, 4(2 + 9) = 44; 5(9 + 44) = 265; and so on.</p> + +<hr style="width: 30%;" /> +<p><a name="X_268_THE_PEAL_OF_BELLSa" id="X_268_THE_PEAL_OF_BELLSa"></a><a href="#X_268_THE_PEAL_OF_BELLS"><b>268.—THE PEAL OF BELLS.—<i>solution</i></b></a></p> + +<p>The bells should be rung as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>1 2 3 4</td></tr> +<tr><td align='center'>2 1 4 3</td></tr> +<tr><td align='center'>2 4 1 3</td></tr> +<tr><td align='center'>4 2 3 1</td></tr> +<tr><td align='center'>4 3 2 1</td></tr> +<tr><td align='center'>3 4 1 2</td></tr> +<tr><td align='center'>3 1 4 2</td></tr> +<tr><td align='center'>1 3 2 4</td></tr> +<tr><td align='center'>3 1 2 4</td></tr> +<tr><td align='center'>1 3 4 2</td></tr> +<tr><td align='center'>1 4 3 2</td></tr> +<tr><td align='center'>4 1 2 3</td></tr> +<tr><td align='center'>4 2 1 3</td></tr> +<tr><td align='center'>2 4 3 1</td></tr> +<tr><td align='center'>2 3 4 1</td></tr> +<tr><td align='center'>3 2 1 4</td></tr> +<tr><td align='center'>2 3 1 4</td></tr> +<tr><td align='center'>3 2 4 1</td></tr> +<tr><td align='center'>3 4 2 1</td></tr> +<tr><td align='center'>4 3 1 2</td></tr> +<tr><td align='center'>4 1 3 2</td></tr> +<tr><td align='center'>1 4 2 3</td></tr> +<tr><td align='center'>1 2 4 3</td></tr> +<tr><td align='center'>2 1 3 4</td></tr> +</table></div> + +<p>I have constructed peals for five and six bells respectively, and a +solution is possible for any number of bells under the conditions +previously stated.</p> + +<hr style="width: 30%;" /> +<p><a name="X_269_THREE_MEN_IN_A_BOATa" id="X_269_THREE_MEN_IN_A_BOATa"></a><a href="#X_269_THREE_MEN_IN_A_BOAT"><b>269.—THREE MEN IN A BOAT.—<i>solution</i></b></a></p> + +<p>If there were no conditions whatever, except that the men were all to +go out together, in threes, they could row in an immense number of +different ways. If the reader wishes to know how many, the number is +455<sup>7</sup>. And with the condition that no two may ever be together more +than once, there are no fewer than 15,567,552,000 different +solutions—that is, different ways of arranging the men. With one +solution before him, the reader will realize why this must be, for +although, as an example, A must go out once with B and once with C, it +does not necessarily follow that he must go out with C on the same +occasion that he goes with B. He might take any other letter with him +on that occasion, though the fact of his taking other than B would +have its effect on the arrangement of the other triplets.</p> + +<p>Of course only a certain number of all these arrangements are +available when we have that other condition of using the smallest +possible number of boats. As a matter of fact we need employ only ten +different boats. Here is one the arrangements:—</p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'></td><td align='center'>1</td><td align='center'>2</td><td align='center'>3</td><td align='center'>4</td><td align='center'>5</td></tr> +<tr><td align='center'>1st Day</td><td align='center'>(ABC)</td><td align='center'>(DBF)</td><td align='center'>(GHI)</td><td align='center'>(JKL)</td><td align='center'>(MNO)</td></tr> +<tr><td align='center'></td><td align='center'>8</td><td align='center'>6</td><td align='center'>7</td><td align='center'>9</td><td align='center'>10</td></tr> +<tr><td align='center'>2nd Day</td><td align='center'>(ADG)</td><td align='center'>(BKN)</td><td align='center'>(COL)</td><td align='center'>(JEI)</td><td align='center'>(MHF)</td></tr> +<tr><td align='center'></td><td align='center'>3</td><td align='center'>5</td><td align='center'>4</td><td align='center'>1</td><td align='center'>2</td></tr> +<tr><td align='center'>3rd Day</td><td align='center'>(AJM)</td><td align='center'>(BEH)</td><td align='center'>(CFI)</td><td align='center'>(DKO)</td><td align='center'>(GNL)</td></tr> +<tr><td align='center'></td><td align='center'>7</td><td align='center'>6</td><td align='center'>8</td><td align='center'>9</td><td align='center'>1</td></tr> +<tr><td align='center'>4th Day</td><td align='center'>(AEK)</td><td align='center'>(CGM)</td><td align='center'>(BOI)</td><td align='center'>(DHL)</td><td align='center'>(JNF)</td></tr> +<tr><td align='center'></td><td align='center'>4</td><td align='center'>5</td><td align='center'>3</td><td align='center'>10</td><td align='center'>2</td></tr> +<tr><td align='center'>5th Day</td><td align='center'>(AHN)</td><td align='center'>(CDJ)</td><td align='center'>(BFL)</td><td align='center'>(GEO)</td><td align='center'>(MKI)</td></tr> +<tr><td align='center'></td><td align='center'>6</td><td align='center'>7</td><td align='center'>8</td><td align='center'>10</td><td align='center'>1</td></tr> +<tr><td align='center'>6th Day</td><td align='center'>(AFO)</td><td align='center'>(BGJ)</td><td align='center'>(CKH)</td><td align='center'>(DNI)</td><td align='center'>(MEL)</td></tr> +<tr><td align='center'></td><td align='center'>5</td><td align='center'>4</td><td align='center'>3</td><td align='center'>9</td><td align='center'>2</td></tr> +<tr><td align='center'>7th Day</td><td align='center'>(AIL)</td><td align='center'>(BDM)</td><td align='center'>(CEN)</td><td align='center'>(GKF)</td><td align='center'>(JHO)</td></tr> +</table></div> + +<p>It will be found that no two men ever go out twice together, and that +no man ever goes out twice in the same boat.</p> + +<p>This is an extension of the well-known problem of the "Fifteen +Schoolgirls," by Kirkman. The original conditions were simply that +fifteen girls walked out on seven days in triplets without any girl +ever walking twice in a triplet with another girl. Attempts at a +general solution of this puzzle had exercised the ingenuity of +mathematicians since 1850, when the question was first propounded, +until recently. In 1908 and the two following years I indicated (see +<i>Educational Times Reprints</i>, Vols. XIV., XV., and XVII.) that all our +trouble had arisen from a failure to discover that 15 is a special +case (too small to enter into the general law for all higher numbers +of girls of the form 6<i>n</i> + 3), and showed what that general law is and +how the groups should be posed for any number of girls. I gave actual +arrangements for numbers that had previously baffled all attempts to +manipulate, and the problem may now be considered generally solved. +Readers will find an excellent full account of the puzzle in W.W. +Rouse Ball's <i>Mathematical Recreations</i>, 5th edition.</p> + +<hr style="width: 30%;" /> +<p><a name="X_270_THE_GLASS_BALLSa" id="X_270_THE_GLASS_BALLSa"></a><a href="#X_270_THE_GLASS_BALLS"><b>270.—THE GLASS BALLS.—<i>solution</i></b></a></p> + +<p>There are, in all, sixteen balls to be broken, or sixteen places in +the order of breaking. Call the four strings A, B, C, and D—order is +here of no importance. The breaking of the balls on A may occupy any 4 +out of these 16 places—that is, the combinations of 16 things, taken +4 together, will be</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' class='bb'>13 × 14 × 15 × 16</td><td align='center' rowspan='2'> = 1,820</td></tr> +<tr><td align='center'>1 × 2 × 3 × 4</td></tr> +</table></div> + +<p>ways for A. In every one of these cases B may occupy any 4 out of the +remaining 12 places, making</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' class='bb'>9 × 10 × 11 × 12</td><td align='center' rowspan='2'> = 495</td></tr> +<tr><td align='center'>1 × 2 × 3 × 4</td></tr> +</table></div> + +<p>ways. Thus 1,820 × 495 = 900,900 different placings are open to A and B. +But for every one of these cases C may occupy</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' class='bb'>5 × 6 × 7 × 8</td><td align='center' rowspan='2'> = 70</td></tr> +<tr><td align='center'>1 × 2 × 3 × 4</td></tr> +</table></div> + + +<p>different places; so that 900,900 × 70 = 63,063,000 different placings are +open to A, B, and C. In every one of these cases, D has no choice but +to take the four places that remain. Therefore the correct answer is +that the balls may be broken in 63,063,000 different ways under the +conditions. Readers should compare this problem with No. 345, "The Two +Pawns," which they will then know how to solve for cases where there +are three, four, or more pawns on the board.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 205<a name="Page_205" id="Page_205"></a></span><a name="X_271_FIFTEEN_LETTER_PUZZLEa" id="X_271_FIFTEEN_LETTER_PUZZLEa"></a><a href="#X_271_FIFTEEN_LETTER_PUZZLE"><b>271.—FIFTEEN LETTER PUZZLE.—<i>solution</i></b></a></p> + +<p>The following will be found to comply with the conditions of +grouping:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>ALE</td><td align='center'>MET</td><td align='center'>MOP</td><td align='center'>BLM</td></tr> +<tr><td align='center'>BAG</td><td align='center'>CAP</td><td align='center'>YOU</td><td align='center'>CLT</td></tr> +<tr><td align='center'>IRE</td><td align='center'>OIL</td><td align='center'>LUG</td><td align='center'>LNR</td></tr> +<tr><td align='center'>NAY</td><td align='center'>BIT</td><td align='center'>BUN</td><td align='center'>BPR</td></tr> +<tr><td align='center'>AIM</td><td align='center'>BEY</td><td align='center'>RUM</td><td align='center'>GMY</td></tr> +<tr><td align='center'>OAR</td><td align='center'>GIN</td><td align='center'>PLY</td><td align='center'>CGR</td></tr> +<tr><td align='center'>PEG</td><td align='center'>ICY</td><td align='center'>TRY</td><td align='center'>CMN</td></tr> +<tr><td align='center'>CUE</td><td align='center'>COB</td><td align='center'>TAU</td><td align='center'>PNT</td></tr> +<tr><td align='center'>ONE</td><td align='center'>GOT</td><td align='center'>PIU</td></tr> +</table></div> + +<p>The fifteen letters used are A, E, I, O, U, Y, and B, C, G, L, M, N, +P, R, T. The number of words is 27, and these are all shown in the +first three columns. The last word, PIU, is a musical term in common +use; but although it has crept into some of our dictionaries, it is +Italian, meaning "a little; slightly." The remaining twenty-six are +good words. Of course a TAU-cross is a T-shaped cross, also called the +cross of St. Anthony, and borne on a badge in the Bishop's Palace at +Exeter. It is also a name for the toad-fish.</p> + +<p>We thus have twenty-six good words and one doubtful, obtained under +the required conditions, and I do not think it will be easy to improve +on this answer. Of course we are not bound by dictionaries but by +common usage. If we went by the dictionary only in a case of this +kind, we should find ourselves involved in prefixes, contractions, and +such absurdities as I.O.U., which Nuttall actually gives as a word.</p> + +<hr style="width: 30%;" /> +<p><a name="X_272_THE_NINE_SCHOOLBOYSa" id="X_272_THE_NINE_SCHOOLBOYSa"></a><a href="#X_272_THE_NINE_SCHOOLBOYS"><b>272.—THE NINE SCHOOLBOYS.—<i>solution</i></b></a></p> + +<p>The boys can walk out as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>1st Day.</td><td align='center'>2nd Day.</td><td align='center'>3rd Day.</td><td align='center'>4th Day.</td><td align='center'>5th Day.</td><td align='center'>6th Day.</td></tr> +<tr><td align='center'>A B C</td><td align='center'>B F H</td><td align='center'>F A G</td><td align='center'>A D H</td><td align='center'>G B I</td><td align='center'>D C A</td></tr> +<tr><td align='center'>D E F</td><td align='center'>E I A</td><td align='center'>I D B</td><td align='center'>B E G</td><td align='center'>C F D</td><td align='center'>E H B</td></tr> +<tr><td align='center'>G H I</td><td align='center'>C G D</td><td align='center'>H C E</td><td align='center'>F I C</td><td align='center'>H A E</td><td align='center'>I G F</td></tr> +</table></div> + +<p>Every boy will then have walked by the side of every other boy once +and once only.</p> + +<p>Dealing with the problem generally, 12<i>n</i> + 9 boys may walk out in +triplets under the conditions on 9<i>n</i> + 6 days, where n may be nought or +any integer. Every possible pair will occur once. Call the number of +boys <i>m</i>. Then every boy will pair <i>m</i> - 1 times, of which <sup>(<i>m</i> - 1)</sup>/<sub>4</sub> times he +will be in the middle of a triplet and <sup>(<i>m</i> - 1)</sup>/<sub>2</sub> times on the outside. +Thus, if we refer to the solution above, we find that every boy is in +the middle twice (making 4 pairs) and four times on the outside +(making the remaining 4 pairs of his 8). The reader may now like to +try his hand at solving the two next cases of 21 boys on 15 days, and +33 boys on 24 days. It is, perhaps, interesting to note that a school +of 489 boys could thus walk out daily in one leap year, but it would +take 731 girls (referred to in the solution to No. 269) to perform +their particular feat by a daily walk in a year of 365 days.</p> + +<hr style="width: 30%;" /> +<p><a name="X_273_THE_ROUND_TABLEa" id="X_273_THE_ROUND_TABLEa"></a><a href="#X_273_THE_ROUND_TABLE"><b>273.—THE ROUND TABLE.—<i>solution</i></b></a></p> + +<p>The history of this problem will be found in <i>The Canterbury Puzzles</i> +(No. 90). Since the publication of that book in 1907, so far as I +know, nobody has succeeded in solving the case for that unlucky number +of persons, 13, seated at a table on 66 occasions. A solution is +possible for any number of persons, and I have recorded schedules for +every number up to 25 persons inclusive and for 33. But as I know a +good many mathematicians are still considering the case of 13, I will +not at this stage rob them of the pleasure of solving it by showing +the answer. But I will now display the solutions for all the cases up +to 12 persons inclusive. Some of these solutions are now published for +the first time, and they may afford useful clues to investigators.</p> + +<p>The solution for the case of 3 persons seated on 1 occasion needs no +remark.</p> + +<p>A solution for the case of 4 persons on 3 occasions is as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>1 2 3 4</td></tr> +<tr><td align='center'>1 3 4 2</td></tr> +<tr><td align='center'>1 4 2 3</td></tr> +</table></div> + +<p>Each line represents the order for a sitting, and the person +represented by the last number in a line must, of course, be regarded +as sitting next to the first person in the same line, when placed at +the round table.</p> + +<p>The case of 5 persons on 6 occasions may be solved as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>1 2 3 4 5</td></tr> +<tr><td align='center'>1 2 4 5 3</td></tr> +<tr><td align='center'>1 2 5 3 4</td></tr> +<tr><td align='center'>1 3 2 5 4</td></tr> +<tr><td align='center'>1 4 2 3 5</td></tr> +<tr><td align='center'>1 5 2 4 3</td></tr> +</table></div> + +<p>The case for 6 persons on 10 occasions is solved thus:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>1 2 3 6 4 5</td></tr> +<tr><td align='center'>1 3 4 2 5 6</td></tr> +<tr><td align='center'>1 4 5 3 6 2</td></tr> +<tr><td align='center'>1 5 6 4 2 3</td></tr> +<tr><td align='center'>1 6 2 5 3 4</td></tr> +<tr><td align='center'>1 2 4 5 6 3</td></tr> +<tr><td align='center'>1 3 5 6 2 4</td></tr> +<tr><td align='center'>1 4 6 2 3 5</td></tr> +<tr><td align='center'>1 5 2 3 4 6</td></tr> +<tr><td align='center'>1 6 3 4 5 2</td></tr> +</table></div> + +<p>It will now no longer be necessary to give the solutions in full, for +reasons that I will explain. It will be seen in the examples above +that the 1 (and, in the case of 5 persons, also the 2) <span class='pagenum'>Pg 206<a name="Page_206" id="Page_206"></a></span>is repeated +down the column. Such a number I call a "repeater." The other numbers +descend in cyclical order. Thus, for 6 persons we get the cycle, 2, 3, +4, 5, 6, 2, and so on, in every column. So it is only necessary to +give the two lines 1 2 3 6 4 5 and 1 2 4 5 6 3, and denote the cycle +and repeaters, to enable any one to write out the full solution +straight away. The reader may wonder why I do not start the last +solution with the numbers in their natural order, 1 2 3 4 5 6. If I +did so the numbers in the descending cycle would not be in their +natural order, and it is more convenient to have a regular cycle than +to consider the order in the first line.</p> + +<p>The difficult case of 7 persons on 15 occasions is solved as follows, +and was given by me in <i>The Canterbury Puzzles</i>:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>1 2 3 4 5 7 6</td></tr> +<tr><td align='center'>1 6 2 7 5 3 4</td></tr> +<tr><td align='center'>1 3 5 2 6 7 4</td></tr> +<tr><td align='center'>1 5 7 4 3 6 2</td></tr> +<tr><td align='center'>1 5 2 7 3 4 6</td></tr> +</table></div> + +<p>In this case the 1 is a repeater, and there are <i>two</i> separate cycles, +2, 3, 4, 2, and 5, 6, 7, 5. We thus get five groups of three lines +each, for a fourth line in any group will merely repeat the first +line.</p> + +<p>A solution for 8 persons on 21 occasions is as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>1 8 6 3 4 5 2 7</td></tr> +<tr><td align='center'>1 8 4 5 7 2 3 6</td></tr> +<tr><td align='center'>1 8 2 7 3 6 4 5</td></tr> +</table></div> + +<p>The 1 is here a repeater, and the cycle 2, 3, 4, 5, 6, 7, 8. Every one +of the 3 groups will give 7 lines.</p> + +<p>Here is my solution for 9 persons on 28 occasions:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>2 1 9 7 4 5 6 3 8</td></tr> +<tr><td align='center'>2 9 5 1 6 8 3 4 7</td></tr> +<tr><td align='center'>2 9 3 1 8 4 7 5 6</td></tr> +<tr><td align='center'>2 9 1 5 6 4 7 8 3</td></tr> +</table></div> + +<p>There are here two repeaters, 1 and 2, and the cycle is 3, 4, 5, 6, 7, +8, 9. We thus get 4 groups of 7 lines each.</p> + +<p>The case of 10 persons on 36 occasions is solved as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>1 10 8 3 6 5 4 7 2 9</td></tr> +<tr><td align='center'>1 10 6 5 2 9 7 4 3 8</td></tr> +<tr><td align='center'>1 10 2 9 3 8 6 5 7 4</td></tr> +<tr><td align='center'>1 10 7 4 8 3 2 9 5 6</td></tr> +</table></div> + +<p>The repeater is 1, and the cycle, 2, 3, 4, 5, 6, 7, 8, 9, 10. We here +have 4 groups of 9 lines each.</p> + +<p>My solution for 11 persons on 45 occasions is as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>2</td><td align='right'>11</td><td align='right'>9</td><td align='right'>4</td><td align='right'>7</td><td align='right'>6</td><td align='right'>5</td><td align='right'>1</td><td align='right'>8</td><td align='right'>3</td><td align='right'>10</td></tr> +<tr><td align='right'>2</td><td align='right'>1</td><td align='right'>11</td><td align='right'>7</td><td align='right'>6</td><td align='right'>3</td><td align='right'>10</td><td align='right'>8</td><td align='right'>5</td><td align='right'>4</td><td align='right'>9</td></tr> +<tr><td align='right'>2</td><td align='right'>11</td><td align='right'>10</td><td align='right'>3</td><td align='right'>9</td><td align='right'>4</td><td align='right'>8</td><td align='right'>5</td><td align='right'>1</td><td align='right'>7</td><td align='right'>6</td></tr> +<tr><td align='right'>2</td><td align='right'>11</td><td align='right'>5</td><td align='right'>8</td><td align='right'>1</td><td align='right'>3</td><td align='right'>10</td><td align='right'>6</td><td align='right'>7</td><td align='right'>9</td><td align='right'>4</td></tr> +<tr><td align='right'>2</td><td align='right'>11</td><td align='right'>1</td><td align='right'>10</td><td align='right'>3</td><td align='right'>4</td><td align='right'>9</td><td align='right'>6</td><td align='right'>7</td><td align='right'>5</td><td align='right'>8</td></tr> +</table></div> + +<p>There are two repeaters, 1 and 2, and the cycle is, 3, 4, 5,... 11. We +thus get 5 groups of 9 lines each.</p> + +<p>The case of 12 persons on 55 occasions is solved thus:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>1</td><td align='right'>2</td><td align='right'>3</td><td align='right'>12</td><td align='right'>4</td><td align='right'>11</td><td align='right'>5</td><td align='right'>10</td><td align='right'>6</td><td align='right'>9</td><td align='right'>7</td><td align='right'>8</td></tr> +<tr><td align='right'>1</td><td align='right'>2</td><td align='right'>4</td><td align='right'>11</td><td align='right'>6</td><td align='right'>9</td><td align='right'>8</td><td align='right'>7</td><td align='right'>10</td><td align='right'>5</td><td align='right'>12</td><td align='right'>3</td></tr> +<tr><td align='right'>1</td><td align='right'>2</td><td align='right'>5</td><td align='right'>10</td><td align='right'>8</td><td align='right'>7</td><td align='right'>11</td><td align='right'>4</td><td align='right'>3</td><td align='right'>12</td><td align='right'>6</td><td align='right'>9</td></tr> +<tr><td align='right'>1</td><td align='right'>2</td><td align='right'>6</td><td align='right'>9</td><td align='right'>10</td><td align='right'>5</td><td align='right'>3</td><td align='right'>12</td><td align='right'>7</td><td align='right'>8</td><td align='right'>11</td><td align='right'>4</td></tr> +<tr><td align='right'>1</td><td align='right'>2</td><td align='right'>7</td><td align='right'>8</td><td align='right'>12</td><td align='right'>3</td><td align='right'>6</td><td align='right'>9</td><td align='right'>11</td><td align='right'>4</td><td align='right'>5</td><td align='right'>10</td></tr> +</table></div> + +<p>Here 1 is a repeater, and the cycle is 2, 3, 4, 5,... 12. We thus get +5 groups of 11 lines each.</p> + +<hr style="width: 30%;" /> +<p><a name="X_274_THE_MOUSE-TRAP_PUZZLEa" id="X_274_THE_MOUSE-TRAP_PUZZLEa"></a><a href="#X_274_THE_MOUSE-TRAP_PUZZLE"><b>274.—THE MOUSE-TRAP PUZZLE.—<i>solution</i></b></a></p> + +<p>If we interchange cards 6 and 13 and begin our count at 14, we may +take up all the twenty-one cards—that is, make twenty-one +"catches"—in the following order: 6, 8, 13, 2, 10, 1, 11, 4, 14, 3, +5, 7, 21, 12, 15, 20, 9, 16, 18, 17, 19. We may also exchange 10 and +14 and start at 16, or exchange 6 and 8 and start at 19.</p> + +<hr style="width: 30%;" /> +<p><a name="X_275_THE_SIXTEEN_SHEEPa" id="X_275_THE_SIXTEEN_SHEEPa"></a><a href="#X_275_THE_SIXTEEN_SHEEP"><b>275.—THE SIXTEEN SHEEP.—<i>solution</i></b></a></p> + +<p>The six diagrams on next page show solutions for the cases where we +replace 2, 3, 4, 5, 6, and 7 hurdles. The dark lines indicate the +hurdles that have been replaced. There are, of course, other ways of +making the removals.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a275.png" width="600" height="413" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_276_THE_EIGHT_VILLASa" id="X_276_THE_EIGHT_VILLASa"></a><a href="#X_276_THE_EIGHT_VILLAS"><b>276.—THE EIGHT VILLAS.—<i>solution</i></b></a></p> + +<p>There are several ways of solving the puzzle, but there is very little +difference between them. The solver should, however, first of all bear +in mind that in making his calculations he need only consider the four +villas that stand at the corners, because the intermediate villas can +never vary when the corners are known. One way is to place the numbers +nought to 9 one at a time in the top left-hand corner, and then +consider each case in turn.</p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/a276.png" width="500" height="343" alt="" title="" /> +</div> + +<p>Now, if we place 9 in the corner as shown in the Diagram A, two of the +corners cannot be occupied, while the corner that is diagonally +opposite may be filled by 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9 persons. We +thus see that there are 10<span class='pagenum'>Pg 207<a name="Page_207" id="Page_207"></a></span> +solutions with a 9 in the corner. If, however, we substitute 8, the +two corners in the same row and column may contain 0, 0, or 1, 1, or +0, 1, or 1, 0. In the case of B, ten different selections may be made +for the fourth corner; but in each of the cases C, D, and E, only nine +selections are possible, because we cannot use the 9. Therefore with 8 +in the top left-hand corner there are 10 + (3 × 9) = 37 different +solutions. If we then try 7 in the corner, the result will be 10 + 27 ++ 40, or 77 solutions. With 6 we get 10 + 27 + 40 + 49 = 126; with 5, +10 + 27 + 40 + 49 + 54 = 180; with 4, the same as with 5, + 55 = 235 +; with 3, the same as with 4, + 52 = 287; with 2, the same as with 3, ++ 45 = 332; with 1, the same as with 2, + 34 = 366, and with nought in +the top left-hand corner the number of solutions will be found to be +10 + 27 + 40 + 49 + 54 + 55 + 52 + 45 + 34 + 19 = 385. As there is no +other number to be placed in the top left-hand corner, we have now +only to add these totals together thus, 10 + 37 + 77 + 126 + 180 + 235 ++ 287 + 332 + 366 + 385 = 2,035. We therefore find that the total +number of ways in which tenants may occupy some or all of the eight +villas so that there shall be always nine persons living along each +side of the square is 2,035. Of course, this method must obviously +cover all the reversals and reflections, since each corner in turn is +occupied by every number in all possible combinations with the other +two corners that are in line with it.</p> + +<p>Here is a general formula for solving the puzzle: <sup>(<i>n</i>² + 3<i>n</i> + +2)(<i>n</i>² + 3<i>n</i> + 3)</sup>/<sub>6</sub>. Whatever may be the stipulated number of +residents along each of the sides (which number is represented by +<i>n</i>), the total number of different arrangements may be thus +ascertained. In our particular case the number of residents was nine. +Therefore (81 + 27 + 2) × (81 + 27 + 3) and the product, divided by 6, +gives 2,035. If the number of residents had been 0, 1, 2, 3, 4, 5, 6, +7, or 8, the total arrangements would be 1, 7, 26, 70, 155, 301, 532, +876, or 1,365 respectively.</p> + +<hr style="width: 30%;" /> +<p><a name="X_277_COUNTER_CROSSESa" id="X_277_COUNTER_CROSSESa"></a><a href="#X_277_COUNTER_CROSSES"><b>277.—COUNTER CROSSES.—<i>solution</i></b></a></p> + +<p>Let us first deal with the Greek Cross. There are +just eighteen forms in which the numbers may be paired for the two +arms. Here they are:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>12978</td><td align='center'>13968</td><td align='center'>14958</td></tr> +<tr><td align='center'>34956</td><td align='center'>24957</td><td align='center'>23967</td></tr> +<tr><td align='center'>23958</td><td align='center'>13769</td><td align='center'>14759</td></tr> +<tr><td align='center'>14967</td><td align='center'>24758</td><td align='center'>23768</td></tr> +<tr><td align='center'>12589</td><td align='center'>23759</td><td align='center'>13579</td></tr> +<tr><td align='center'>34567</td><td align='center'>14768</td><td align='center'>24568</td></tr> +<tr><td align='center'>14569</td><td align='center'>23569</td><td align='center'>14379</td></tr> +<tr><td align='center'>23578</td><td align='center'>14578</td><td align='center'>25368</td></tr> +<tr><td align='center'>15369</td><td align='center'>24369</td><td align='center'>23189</td></tr> +<tr><td align='center'>24378</td><td align='center'>15378</td><td align='center'>45167</td></tr> +<tr><td align='center'>24179</td><td align='center'>25169</td><td align='center'>34169</td></tr> +<tr><td align='center'>35168</td><td align='center'>34178</td><td align='center'>25178</td></tr> +</table></div> + +<p><span class='pagenum'>Pg 208<a name="Page_208" id="Page_208"></a></span>Of course, the number in the middle is common to both arms. The first +pair is the one I gave as an example. I will suppose that we have +written out all these crosses, always placing the first row of a pair +in the upright and the second row in the horizontal arm. Now, if we +leave the central figure fixed, there are 24 ways in which the numbers +in the upright may be varied, for the four counters may be changed in +1 × 2 × 3 × 4 = 24 ways. And as the four in the horizontal may also be +changed in 24 ways for every arrangement on the other arm, we find +that there are 24 × 24 = 576 variations for every form; therefore, as +there are 18 forms, we get 18 × 576 = 10,368 ways. But this will +include half the four reversals and half the four reflections that we +barred, so we must divide this by 4 to obtain the correct answer to +the Greek Cross, which is thus 2,592 different ways. The division is +by 4 and not by 8, because we provided against half the reversals and +reflections by always reserving one number for the upright and the +other for the horizontal.</p> + +<p>In the case of the Latin Cross, it is obvious that we have to deal +with the same 18 forms of pairing. The total number of different ways +in this case is the full number, 18 × 576. Owing to the fact that the +upper and lower arms are unequal in length, permutations will repeat +by reflection, but not by reversal, for we cannot reverse. Therefore +this fact only entails division by 2. But in every pair we may +exchange the figures in the upright with those in the horizontal +(which we could not do in the case of the Greek Cross, as the arms are +there all alike); consequently we must multiply by 2. This +multiplication by 2 and division by 2 cancel one another. Hence 10,368 +is here the correct answer.</p> + +<hr style="width: 30%;" /> +<p><a name="X_278_A_DORMITORY_PUZZLEa" id="X_278_A_DORMITORY_PUZZLEa"></a><a href="#X_278_A_DORMITORY_PUZZLE"><b>278.—A DORMITORY PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a278.png" width="400" height="276" alt="" title="" /> +</div> + +<p>Arrange the nuns from day to day as shown in the six diagrams. The +smallest possible number of nuns would be thirty-two, and the +arrangements on the last three days admit of variation.</p> + +<hr style="width: 30%;" /> +<p><a name="X_279_THE_BARRELS_OF_BALSAMa" id="X_279_THE_BARRELS_OF_BALSAMa"></a><a href="#X_279_THE_BARRELS_OF_BALSAM"><b>279.—THE BARRELS OF BALSAM.—<i>solution</i></b></a></p> + +<p>This is quite easy to solve for any number of barrels—if you know +how. This is the way to do it. There are five barrels in each row +Multiply the numbers 1, 2, 3, 4, 5 together; and also multiply 6, 7, +8, 9, 10 together. Divide one result by the other, and we get the +number of different combinations or selections of ten things taken +five at a time. This is here 252. Now, if we divide this by 6 (1 more +than the number in the row) we get 42, which is the correct answer to +the puzzle, for there are 42 different ways of arranging the barrels. +Try this method of solution in the case of six barrels, three in each +row, and you will find the answer is 5 ways. If you check this by +trial, you will discover the five arrangements with 123, 124, 125, +134, 135 respectively in the top row, and you will find no others.</p> + +<p>The general solution to the problem is, in fact, this:</p> + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="0" summary=""> +<tr><td align='center' rowspan='2' class='bb'><div style="font-size: larger"><b>C</b></div></td><td align='center'><sub>n</sub></td></tr> +<tr><td align='center' class='bb'><sup>2<i>n</i></sup></td></tr> +<tr><td align='center' colspan='2'><i>n</i> + 1</td></tr> +</table></div> + +<p>where 2<i>n</i> equals the number of barrels. The symbol <b>C</b>, of course, +implies that we have to find how many combinations, or selections, we +can make of 2<i>n</i> things, taken <i>n</i> at a time.</p> + +<hr style="width: 30%;" /> +<p><a name="X_280_BUILDING_THE_TETRAHEDRONa" id="X_280_BUILDING_THE_TETRAHEDRONa"></a><a href="#X_280_BUILDING_THE_TETRAHEDRON"><b>280.—BUILDING THE TETRAHEDRON.—<i>solution</i></b></a></p> + +<p>Take your constructed pyramid and hold it so that one stick only lies +on the table. Now, four sticks must branch off from it in different +directions—two at each end. Any one of the five sticks may be left +out of this connection; therefore the four may be selected in 5 +different ways. But these four matches may be placed in 24 different +orders. And as any match may be joined at either of its ends, they may +further be varied (after their situations are settled for any +particular arrangement) in 16 different ways. In every arrangement the +sixth stick may be added in 2 different ways. Now multiply these +results together, and we get 5 × 24 × 16 × 2 = 3,840 as the exact +number of ways in which the pyramid may be constructed. This method +excludes all possibility of error.</p> + +<p>A common cause of error is this. If you calculate your combinations by +working upwards from a basic triangle lying on the table, you will get +half the correct number of ways, because you overlook the fact that an +equal number of pyramids may be built on that triangle downwards, so +to speak, through the table. They are, in fact, reflections of the +others, and examples from the two sets of pyramids cannot be set up to +resemble one another—except under fourth dimensional conditions!</p> + +<hr style="width: 30%;" /> +<p><a name="X_281_PAINTING_A_PYRAMIDa" id="X_281_PAINTING_A_PYRAMIDa"></a><a href="#X_281_PAINTING_A_PYRAMID"><b>281.—PAINTING A PYRAMID.—<i>solution</i></b></a></p> + +<p>It will be convenient to imagine that we are painting our pyramids on +the flat cardboard, as in the diagrams, before folding up. Now, if we +take any <i>four</i> colours (say red, blue, green, and yellow), they may +be applied in only 2 distinctive ways, as shown in Figs, 1 and 2. Any +other way will only result in one of these when the pyramids are +folded up. If we take any <i>three</i> colours, they may be applied in the +3 ways shown in Figs. 3, 4, and 5. If we take any <i>two</i> colours, they +may be applied in the 3 <span class='pagenum'>Pg 209<a name="Page_209" id="Page_209"></a></span>ways shown in Figs. 6, 7, and 8. If we take +any <i>single</i> colour, it may obviously be applied in only 1 way. But +four colours may be selected in 35 ways out of seven; three in 35 +ways; two in 21 ways; and one colour in 7 ways. Therefore 35 applied +in 2 ways = 70; 35 in 3 ways = 105; 21 in 3 ways = 63; and 7 in 1 way += 7. Consequently the pyramid may be painted in 245 different ways (70 ++ 105 + 63 + 7), using the seven colours of the solar spectrum in +accordance with the conditions of the puzzle.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a281.png" width="400" height="345" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_282_THE_ANTIQUARYS_CHAINa" id="X_282_THE_ANTIQUARYS_CHAINa"></a><a href="#X_282_THE_ANTIQUARYS_CHAIN"><b>282.—THE ANTIQUARY'S CHAIN.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a282.png" width="400" height="239" alt="" title="" /> +</div> + +<p>The number of ways in which nine things may be arranged in a row +without any restrictions is 1 × 2 × 3 × 4 × 5 × 6 × 7 × 8 × 9 = +362,880. But we are told that the two circular rings must never be +together; therefore we must deduct the number of times that this would +occur. The number is 1 × 2 × 3 × 4 × 5 × 6 × 7 × 8 = 40,320 × 2 = +80,640, because if we consider the two circular links to be +inseparably joined together they become as one link, and eight links +are capable of 40,320 arrangements; but as these two links may always +be put on in the orders AB or BA, we have to double this number, it +being a question of arrangement and not of design. The deduction +required reduces our total to 282,240. Then one of our links is of a +peculiar form, like an 8. We have therefore the option of joining on +either one end or the other on every occasion, so we must double the +last result. This brings up our total to 564,480.</p> + +<p>We now come to the point to which I directed the reader's +attention—that every link may be put on in one of two ways. If we +join the first finger and thumb of our left hand horizontally, and +then link the first finger and thumb of the right hand, we see that +the right thumb may be either above or below. But in the case of our +chain we must remember that although that 8-shaped link has two +independent <i>ends</i> it is like every other link in having only two +<i>sides</i>—that is, you cannot turn over one end without turning the +other at the same time.</p> + +<p>We will, for convenience, assume that each link has a black side and a +side painted white. Now, if it were stipulated that (with the chain +lying on the table, and every successive link falling over its +predecessor in the same way, as in the diagram) only the white sides +should be uppermost as in A, then the answer would be 564,480, as +above—ignoring for the present all reversals of the completed chain. +If, however, the first link were allowed to be placed either side up, +then we could have either A or B, and the answer would be 2 × 564,480 += 1,128,960; if two links might be placed either way up, the answer +would be 4 × 564,480; if three links, then 8 × 564,480, and so on. +Since, therefore, every link may be placed either side up, the number +will be 564,480 multiplied by 2<sup>9</sup>, or by 512. This raises our total to +289,013,760.</p> + +<p>But there is still one more point to be considered. We have not yet +allowed for the fact that with any given arrangement three of the +other arrangements may be obtained by simply turning the chain over +through its entire length and by reversing the ends. Thus C is really +the same as A, and if we turn this page upside down, then A and C give +two other arrangements that are still really identical. Thus to get +the correct answer to the puzzle we must divide our last total by 4, +when we find that there are just 72,253,440 different ways in which +the smith might have put those links together. In other words, if the +nine links had originally formed a piece of chain, and it was known +that the two circular links were separated, then it would be +72,253,439 chances to 1 that the smith would not have put the links +together again precisely as they were arranged before!</p> + +<hr style="width: 30%;" /> +<p><a name="X_283_THE_FIFTEEN_DOMINOESa" id="X_283_THE_FIFTEEN_DOMINOESa"></a><a href="#X_283_THE_FIFTEEN_DOMINOES"><b>283.—THE FIFTEEN DOMINOES.—<i>solution</i></b></a></p> + +<p>The reader may have noticed that at each end of the line I give is a +four, so that, if we like, we can form a ring instead of a line. It +can easily be proved that this must always be so. Every line +arrangement will make a circular arrangement if we like to join the +ends. Now, curious as it may at first appear, the following diagram +exactly represents the conditions when we leave the doubles out of the +question and devote our attention to forming circular arrangements. +Each number, or half domino, is in line with every other number, so +that if we start at any one of the five numbers and go over all the +lines of the pentagon once and once only we shall come back to the +starting place, and the order of our route will give us one of the +circular arrangements for the ten <span class='pagenum'>Pg 210<a name="Page_210" id="Page_210"></a></span>dominoes. Take your pencil and +follow out the following route, starting at the 4: 41304210234. You +have been over all the lines once only, and by repeating all these +figures in this way, 41—13—30—04—42—21—10—02—23—34, you get +an arrangement of the dominoes (without the doubles) which will be +perfectly clear. Take other routes and you will get other +arrangements. If, therefore, we can ascertain just how many of these +circular routes are obtainable from the pentagon, then the rest is +very easy.</p> + +<p>Well, the number of different circular routes over the pentagon is +264. How I arrive at these figures I will not at present explain, +because it would take a lot of space. The dominoes may, therefore, be +arranged in a circle in just 264 different ways, leaving out the +doubles. Now, in any one of these circles the five doubles may be +inserted in 2<sup>5</sup> = 32 different ways. Therefore when we include the +doubles there are 264 × 32 = 8,448 different circular arrangements. +But each of those circles may be broken (so as to form our straight +line) in any one of 15 different places. Consequently, 8,448 × 15 +gives 126,720 different ways as the correct answer to the puzzle.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a283.png" width="400" height="382" alt="" title="" /> +</div> + +<p>I purposely refrained from asking the reader to discover in just how +many different ways the full set of twenty-eight dominoes may be +arranged in a straight line in accordance with the ordinary rules of +the game, left to right and right to left of any arrangement counting +as different ways. It is an exceedingly difficult problem, but the +correct answer is 7,959,229,931,520 ways. The method of solving is +very complex.</p> + +<hr style="width: 30%;" /> +<p><a name="X_284_THE_CROSS_TARGETa" id="X_284_THE_CROSS_TARGETa"></a><a href="#X_284_THE_CROSS_TARGET"><b>284.—THE CROSS TARGET.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a284.png" width="400" height="394" alt="" title="" /> +</div> + +<p>Twenty-one different squares may be selected. Of these nine will be of +the size shown by the four A's in the diagram, four of the size shown +by the B's, four of the size shown by the C's, two of the size shown +by the D's, and two of the size indicated by the upper single A, the +upper single E, the lower single C, and the EB. It is an interesting +fact that you cannot form any one of these twenty-one squares without +using at least one of the six circles marked E.</p> + +<hr style="width: 30%;" /> +<p><a name="X_285_THE_FOUR_POSTAGE_STAMPSa" id="X_285_THE_FOUR_POSTAGE_STAMPSa"></a><a href="#X_285_THE_FOUR_POSTAGE_STAMPS"><b>285.—THE FOUR POSTAGE STAMPS.—<i>solution</i></b></a></p> + +<p>Referring to the original diagram, the four stamps may be given in the +shape 1, 2, 3, 4, in three ways; in the shape 1, 2, 5, 6, in six ways; +in the shape 1, 2, 3, 5, or 1, 2, 3, 7, or 1, 5, 6, 7, or 3, 5, 6, 7, +in twenty-eight ways; in shape 1, 2, 3, 6, or 2, 5, 6, 7, in fourteen +ways; in shape 1, 2, 6, 7, or 2, 3, 5, 6, or 1, 5, 6, 10, or 2, 5, 6, +9, in fourteen ways. Thus there are sixty-five ways in all.</p> + +<hr style="width: 30%;" /> +<p><a name="X_286_PAINTING_THE_DIEa" id="X_286_PAINTING_THE_DIEa"></a><a href="#X_286_PAINTING_THE_DIE"><b>286.—PAINTING THE DIE.—<i>solution</i></b></a></p> + +<p>The 1 can be marked on any one of six different sides. For every side +occupied by 1 we have a selection of four sides for the 2. For every +situation of the 2 we have two places for the 3. (The 6, 5, and 4 need +not be considered, as their positions are determined by the 1, 2, and +3.) Therefore 6, 4, and 2 multiplied together make 48 different +ways—the correct answer.</p> + +<hr style="width: 30%;" /> +<p><a name="X_287_AN_ACROSTIC_PUZZLEa" id="X_287_AN_ACROSTIC_PUZZLEa"></a><a href="#X_287_AN_ACROSTIC_PUZZLE"><b>287.—AN ACROSTIC PUZZLE.—<i>solution</i></b></a></p> + +<p>There are twenty-six letters in the alphabet, giving 325 different +pairs. Every one of these pairs may be reversed, making 650 ways. But +every initial letter may be repeated as the final, producing 26 other +ways. The total is therefore 676 different pairs. In other words, the +answer is the square of the number of letters in the alphabet.</p> + +<hr style="width: 30%;" /> +<p><a name="X_288_CHEQUERED_BOARD_DIVISIONSa" id="X_288_CHEQUERED_BOARD_DIVISIONSa"></a><a href="#X_288_CHEQUERED_BOARD_DIVISIONS"><b>288.—CHEQUERED BOARD DIVISIONS.—<i>solution</i></b></a></p> + +<p>There are 255 different ways of cutting the board into two pieces of +exactly the same size <span class='pagenum'>Pg 211<a name="Page_211" id="Page_211"></a></span>and shape. Every way must involve one of the +five cuts shown in Diagrams A, B, C, D, and E. To avoid repetitions by +reversal and reflection, we need only consider cuts that enter at the +points a, b, and c. But the exit must always be at a point in a +straight line from the entry through the centre. This is the most +important condition to remember. In case B you cannot enter at a, or +you will get the cut provided for in E. Similarly in C or D, you must +not enter the key-line in the same direction as itself, or you will +get A or B. If you are working on A or C and entering at a, you must +consider joins at one end only of the key-line, or you will get +repetitions. In other cases you must consider joins at both ends of +the key; but after leaving a in case D, turn always either to right or +left—use one direction only. Figs. 1 and 2 are examples under A; 3 +and 4 are examples under B; 5 and 6 come under C; <span class='pagenum'>Pg 212<a name="Page_212" id="Page_212"></a></span>and 7 is a pretty example of D. Of course, E is a peculiar type, and +obviously admits of only one way of cutting, for you clearly cannot +enter at b or c.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a288.png" width="600" height="791" alt="" title="" /> +</div> + +<p>Here is a table of the results:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'></td><td></td><td align='center'>a</td><td></td><td align='center'>b</td><td></td><td align='center'>c</td><td></td><td align='center'>Ways.</td></tr> +<tr><td align='right'>A</td><td align='right'>=</td><td align='right'>8</td><td align='right'>+</td><td align='right'>17</td><td align='right'>+</td><td align='right'>21</td><td align='right'>=</td><td align='right'>46</td></tr> +<tr><td align='right'>B</td><td align='right'>=</td><td align='right'>0</td><td align='right'>+</td><td align='right'>17</td><td align='right'>+</td><td align='right'>21</td><td align='right'>=</td><td align='right'>38</td></tr> +<tr><td align='right'>C</td><td align='right'>=</td><td align='right'>15</td><td align='right'>+</td><td align='right'>31</td><td align='right'>+</td><td align='right'>39</td><td align='right'>=</td><td align='right'>85</td></tr> +<tr><td align='right'>D</td><td align='right'>=</td><td align='right'>17</td><td align='right'>+</td><td align='right'>29</td><td align='right'>+</td><td align='right'>39</td><td align='right'>=</td><td align='right'>85</td></tr> +<tr><td align='right'>E</td><td align='right'>=</td><td align='right'>1</td><td align='right'>+</td><td align='right'>0</td><td align='right'>+</td><td align='right'>0</td><td align='right'>=</td><td align='right'>1</td></tr> +<tr><td align='right'></td><td></td><td align='right' class='bt'>41</td><td></td><td align='right' class='bt'>94</td><td></td><td align='right' class='bt'>120</td><td></td><td align='right' class='bt'>255</td></tr> +</table></div> + +<p>I have not attempted the task of enumerating the ways of dividing a +board 8x8—that is, an ordinary chessboard. Whatever the method +adopted, the solution would entail considerable labour.</p> + +<hr style="width: 30%;" /> +<p><a name="X_289_LIONS_AND_CROWNSa" id="X_289_LIONS_AND_CROWNSa"></a><a href="#X_289_LIONS_AND_CROWNS"><b>289.—LIONS AND CROWNS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a289.png" width="400" height="396" alt="" title="" /> +</div> + +<p>Here is the solution. It will be seen that each of the four pieces +(after making the cuts along the thick lines) is of exactly the same +size and shape, and that each piece contains a lion and a crown. Two +of the pieces are shaded so as to make the solution quite clear to the +eye.</p> + +<hr style="width: 30%;" /> +<p><a name="X_290_BOARDS_WITH_AN_ODD_NUMBER_OF_SQUARESa" id="X_290_BOARDS_WITH_AN_ODD_NUMBER_OF_SQUARESa"></a><a href="#X_290_BOARDS_WITH_AN_ODD_NUMBER_OF_SQUARES"><b>290.—BOARDS WITH AN ODD NUMBER OF SQUARES.—<i>solution</i></b></a></p> + +<p>There are fifteen different ways of cutting the 5x5 board (with the +central square removed) into two pieces of the same size and shape. +Limitations of space will not allow me to give diagrams of all these, +but I will enable the reader to draw them all out for himself without +the slightest difficulty. At whatever point on the edge your cut +enters, it must always end at a point on the edge, exactly opposite in +a line through the centre of the square. Thus, if you enter at point 1 +(see Fig. 1) at the top, you must leave at point 1 at the bottom. Now, +1 and 2 are the only two really different points of entry; if we use +any others they will simply produce similar solutions. The directions +of the cuts in the following fifteen</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a290.png" width="400" height="234" alt="" title="" /> +</div> + +<p>solutions are indicated by the numbers on the diagram. The duplication +of the numbers can lead to no confusion, since every successive number +is contiguous to the previous one. But whichever direction you take +from the top downwards you must repeat from the bottom upwards, one +direction being an exact reflection of the other.</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>1, 4, 8.</td></tr> +<tr><td align='left'>1, 4, 3, 7, 8.</td></tr> +<tr><td align='left'>1, 4, 3, 7, 10, 9.</td></tr> +<tr><td align='left'>1, 4, 3, 7, 10, 6, 5, 9.</td></tr> +<tr><td align='left'>1, 4, 5, 9.</td></tr> +<tr><td align='left'>1, 4, 5, 6, 10, 9.</td></tr> +<tr><td align='left'>1, 4, 5, 6, 10, 7, 8.</td></tr> +<tr><td align='left'>2, 3, 4, 8.</td></tr> +<tr><td align='left'>2, 3, 4, 5, 9.</td></tr> +<tr><td align='left'>2, 3, 4, 5, 6, 10, 9.</td></tr> +<tr><td align='left'>2, 3, 4, 5, 6, 10, 7, 8.</td></tr> +<tr><td align='left'>2, 3, 7, 8.</td></tr> +<tr><td align='left'>2, 3, 7, 10, 9.</td></tr> +<tr><td align='left'>2, 3, 7, 10, 6, 5, 9.</td></tr> +<tr><td align='left'>2, 3, 7, 10, 6, 5, 4, 8.</td></tr> +</table></div> + +<p>It will be seen that the fourth direction (1, 4, 3, 7, 10, 6, 5, 9) +produces the solution shown in Fig. 2. The thirteenth produces the +solution given in propounding the puzzle, where the cut entered at the +side instead of at the top. The pieces, however, will be of the same +shape if turned over, which, as it was stated in the conditions, would +not constitute a different solution.</p> + +<hr style="width: 30%;" /> +<p><a name="X_291_THE_GRAND_LAMAS_PROBLEMa" id="X_291_THE_GRAND_LAMAS_PROBLEMa"></a><a href="#X_291_THE_GRAND_LAMAS_PROBLEM"><b>291.—THE GRAND LAMA'S PROBLEM.—<i>solution</i></b></a></p> + +<p>The method of dividing the chessboard so that each of the four parts +shall be of exactly the same size and shape, and contain one of the +gems, is shown in the diagram. The method of shading the squares is +adopted to make the shape of the pieces clear to the eye. Two of the +pieces are shaded and two left white.</p> + +<p>The reader may find it interesting to compare this puzzle with that of +the "Weaver" (No. 14, <i>Canterbury Puzzles</i>).</p> + +<p><span class='pagenum'>Pg 213<a name="Page_213" id="Page_213"></a></span></p><div class="figcenter" style="width: 400px;"> +<img src="images/a291.png" width="400" height="398" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_292_THE_ABBOTS_WINDOWa" id="X_292_THE_ABBOTS_WINDOWa"></a><a href="#X_292_THE_ABBOTS_WINDOW"><b>292.—THE ABBOT'S WINDOW.—<i>solution</i></b></a></p> + +<p>The man who was "learned in strange mysteries" pointed out to Father +John that the orders of the Lord Abbot of St. Edmondsbury might be +easily carried out by blocking up twelve of the lights in the window +as shown by the dark squares in the following sketch:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a292.png" width="400" height="388" alt="" title="" /> +</div> + +<p>Father John held that the four corners should also be darkened, but +the sage explained that it was desired to obstruct no more light than +was absolutely necessary, and he said, anticipating Lord Dundreary, "A +single pane can no more be in a <i>line</i> with itself than one bird can +go into a corner and flock in solitude. The Abbot's condition was that +no diagonal <i>lines</i> should contain an odd number of lights."</p> + +<p>Now, when the holy man saw what had been done he was well pleased, and +said, "Truly, Father John, thou art a man of deep wisdom, in that thou +hast done that which seemed impossible, and yet withal adorned our +window with a device of the cross of St. Andrew, whose name I received +from my godfathers and godmothers." Thereafter he slept well and arose +refreshed. The window might be seen intact to-day in the monastery of +St. Edmondsbury, if it existed, which, alas! the window does not.</p> + +<hr style="width: 30%;" /> +<p><a name="X_293_THE_CHINESE_CHESSBOARDa" id="X_293_THE_CHINESE_CHESSBOARDa"></a><a href="#X_293_THE_CHINESE_CHESSBOARD"><b>293.—THE CHINESE CHESSBOARD.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a293.png" width="400" height="799" alt="" title="" /> +</div> + +<p>Eighteen is the maximum number of pieces. I give two solutions. The +numbered diagram is so cut that the eighteenth piece has the largest +area—eight squares—that is possible under the conditions. The second +diagram was prepared under the added condition that no piece should +contain more than five squares.</p> + +<p>No. 74 in <i>The Canterbury Puzzles</i> shows how to cut the board into +twelve pieces, all differ<span class='pagenum'>Pg 214<a name="Page_214" id="Page_214"></a></span>ent, each containing five squares, with one +square piece of four squares.</p> + +<hr style="width: 30%;" /> +<p><a name="X_294_THE_CHESSBOARD_SENTENCEa" id="X_294_THE_CHESSBOARD_SENTENCEa"></a><a href="#X_294_THE_CHESSBOARD_SENTENCE"><b>294.—THE CHESSBOARD SENTENCE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a294.png" width="400" height="397" alt="" title="" /> +</div> + +<p>The pieces may be fitted together, as shown in the illustration, to +form a perfect chessboard.</p> + +<hr style="width: 30%;" /> +<p><a name="X_295_THE_EIGHT_ROOKSa" id="X_295_THE_EIGHT_ROOKSa"></a><a href="#X_295_THE_EIGHT_ROOKS"><b>295.—THE EIGHT ROOKS.—<i>solution</i></b></a></p> + +<p>Obviously there must be a rook in every row and every column. Starting +with the top row, it is clear that we may put our first rook on any +one of eight different squares. Wherever it is placed, we have the +option of seven squares for the second rook in the second row. Then we +have six squares from which to select the third row, five in the +fourth, and so on. Therefore the number of our different ways must be +8 × 7 × 6 × 5 × 4 × 3 × 2 × 1 = 40,320 (that is 8!), which is the +correct answer.</p> + +<p>How many ways there are if mere reversals and reflections are not +counted as different has not yet been determined; it is a difficult +problem. But this point, on a smaller square, is considered in the +next puzzle.</p> + +<hr style="width: 30%;" /> +<p><a name="X_296_THE_FOUR_LIONSa" id="X_296_THE_FOUR_LIONSa"></a><a href="#X_296_THE_FOUR_LIONS"><b>296.—THE FOUR LIONS.—<i>solution</i></b></a></p> + +<p>There are only seven different ways under the conditions. They are as +follows: 1 2 3 4, 1 2 4 3, 1 3 2 4, 1 3 4 2, 1 4 3 2, 2 1 4 3, 2 4 1 +3. Taking the last example, this notation means that we place a lion +in the second square of first row, fourth square of second row, first +square of third row, and third square of fourth row. The first example +is, of course, the one we gave when setting the puzzle.</p> + +<hr style="width: 30%;" /> +<p><a name="X_297_BISHOPSmdashUNGUARDEDa" id="X_297_BISHOPSmdashUNGUARDEDa"></a><a href="#X_297_BISHOPSmdashUNGUARDED"><b>297.—BISHOPS—UNGUARDED.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a297.png" width="400" height="394" alt="" title="" /> +</div> + +<p>This cannot be done with fewer bishops than eight, and the simplest +solution is to place the bishops in line along the fourth or fifth row +of the board (see diagram). But it will be noticed that no bishop is +here guarded by another, so we consider that point in the next puzzle.</p> + +<hr style="width: 30%;" /> +<p><a name="X_298_BISHOPSmdashGUARDEDa" id="X_298_BISHOPSmdashGUARDEDa"></a><a href="#X_298_BISHOPSmdashGUARDED"><b>298.—BISHOPS—GUARDED.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a298.png" width="400" height="405" alt="" title="" /> +</div> + +<p>This puzzle is quite easy if you first of all give it a little +thought. You need only consider squares of one colour, for whatever +can be done in the case of the white squares can always be repeated on +the black, and they are here quite independent of one another. This +equality, of course, is in consequence of the fact that the number of +squares on an ordinary chessboard, sixty-four, is an even number. If a +square chequered board has an odd number of squares, then there will +always be one more square of one colour than of the other.</p> + +<p>Ten bishops are necessary in order that every square shall be attacked +and every bishop guarded by another bishop. I give one way of +arranging them in the diagram. It will be noticed that the two central +bishops in the group <span class='pagenum'>Pg 215<a name="Page_215" id="Page_215"></a></span>of six on the left-hand side of the board serve +no purpose, except to protect those bishops that are on adjoining +squares. Another solution would therefore be obtained by simply +raising the upper one of these one square and placing the other a +square lower down.</p> + +<hr style="width: 30%;" /> +<p><a name="X_299_BISHOPS_IN_CONVOCATIONa" id="X_299_BISHOPS_IN_CONVOCATIONa"></a><a href="#X_299_BISHOPS_IN_CONVOCATION"><b>299.—BISHOPS IN CONVOCATION.—<i>solution</i></b></a></p> + +<p>The fourteen bishops may be placed in 256 different ways. But every +bishop must always be placed on one of the sides of the board—that +is, somewhere on a row or file on the extreme edge. The puzzle, +therefore, consists in counting the number of different ways that we can +arrange the fourteen round the edge of the board without attack. This is +not a difficult matter. On a chessboard of <i>n</i><sup>2</sup> squares +<i>2n - 2</i> bishops (the maximum number) may always be placed in 2<sup>(<i>n</i>)</sup> ways +without attacking. On an ordinary chessboard <i>n</i> would be 8; therefore +14 bishops may be placed in 256 different ways. It is rather curious +that the general result should come out in so simple a form.</p> + +<hr style="width: 30%;" /> +<p><a name="X_300_THE_EIGHT_QUEENSa" id="X_300_THE_EIGHT_QUEENSa"></a><a href="#X_300_THE_EIGHT_QUEENS"><b>300.—THE EIGHT QUEENS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a300.png" width="400" height="387" alt="" title="" /> +</div> + +<p>The solution to this puzzle is shown in the diagram. It will be found +that no queen attacks another, and also that no three queens are in a +straight line in any oblique direction. This is the only arrangement +out of the twelve fundamentally different ways of placing eight queens +without attack that fulfils the last condition.</p> + +<hr style="width: 30%;" /> +<p><a name="X_301_THE_EIGHT_STARSa" id="X_301_THE_EIGHT_STARSa"></a><a href="#X_301_THE_EIGHT_STARS"><b>301.—THE EIGHT STARS.—<i>solution</i></b></a></p> + +<p>The solution of this puzzle is shown in the first diagram. It is the +only possible solution within the conditions stated. But if one of the +eight stars had not already been placed as shown, there would then +have been eight ways of arranging the stars according to this scheme, +if we count reversals and reflections as different. If you turn this +page round so that each side is in turn at the bottom, you will get +the four reversals; and if you reflect each of these in a mirror, you +will get the four reflections. These are, therefore, merely eight +aspects of one "fundamental solution." But without that first star +being so placed, there is another fundamental solution, as shown in +the second diagram. But this arrangement being in a way symmetrical, +only produces four different aspects by reversal and reflection.</p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/a301.png" width="500" height="242" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_302_A_PROBLEM_IN_MOSAICSa" id="X_302_A_PROBLEM_IN_MOSAICSa"></a><a href="#X_302_A_PROBLEM_IN_MOSAICS"><b>302.—A PROBLEM IN MOSAICS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a302.png" width="400" height="392" alt="" title="" /> +</div> + +<p>The diagram shows how the tiles may be rearranged. As before, one +yellow and one <span class='pagenum'>Pg 216<a name="Page_216" id="Page_216"></a></span>purple tile are dispensed with. I will here point out +that in the previous arrangement the yellow and purple tiles in the +seventh row might have changed places, but no other arrangement was +possible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_303_UNDER_THE_VEILa" id="X_303_UNDER_THE_VEILa"></a><a href="#X_303_UNDER_THE_VEIL"><b>303.—UNDER THE VEIL.—<i>solution</i></b></a></p> + +<p>Some schemes give more diagonal readings of four letters than others, +and we are at first tempted to favour these; but this is a false +scent, because what you appear to gain in this direction you lose in +others. Of course it immediately occurs to the solver that every LIVE +or EVIL is worth twice as much as any other word, since it reads both +ways and always counts as 2. This is an important consideration, +though sometimes those arrangements that contain most readings of +these two words are fruitless in other words, and we lose in the +general count.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a303.png" width="400" height="363" alt="" title="" /> +</div> + +<p>The above diagram is in accordance with the conditions requiring no +letter to be in line with another similar letter, and it gives twenty +readings of the five words—six horizontally, six vertically, four in +the diagonals indicated by the arrows on the left, and four in the +diagonals indicated by the arrows on the right. This is the maximum.</p> + +<p>Four sets of eight letters may be placed on the board of sixty-four +squares in as many as 604 different ways, without any letter ever +being in line with a similar one. This does not count reversals and +reflections as different, and it does not take into consideration the +actual permutations of the letters among themselves; that is, for +example, making the L's change places with the E's. Now it is a +singular fact that not only do the twenty word-readings that I have +given prove to be the real maximum, but there is actually only that +one arrangement from which this maximum may be obtained. But if you +make the V's change places with the I's, and the L's with the E's, in +the solution given, you still get twenty readings—the same number as +before in every direction. Therefore there are two ways of getting the +maximum from the same arrangement. The minimum number of readings is +zero—that is, the letters can be so arranged that no word can be read +in any of the directions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_304_BACHETS_SQUAREa" id="X_304_BACHETS_SQUAREa"></a><a href="#X_304_BACHETS_SQUARE"><b>304.—BACHET'S SQUARE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a304.png" width="400" height="426" alt="" title="" /> +</div> + +<p>Let us use the letters A, K, Q, J, to denote ace, king, queen, jack; +and D, S, H, C, to denote diamonds, spades, hearts, clubs. In Diagrams +1 and 2 we have the two available ways of arranging either group of +letters so that no two similar letters shall be in line—though a +quarter-turn of 1 will give us the arrangement in 2. If we superimpose +or combine these two squares, we get the arrangement of Diagram 3, +which is one solution. But in each square we may put the letters in +the top line in twenty-four different ways without altering the scheme +of arrangement. Thus, in Diagram 4 the S's are similarly placed to the +D's in 2, the H's to the S's, the C's to the H's, and the D's to the +C's. It clearly follows that there must be 24 × 24 = 576 ways of +combining the two primitive arrangements. But the error that Labosne +fell into was that of assuming that the A, K, Q, J must be arranged in +the form 1, and the D, S, H, C in the form 2. He thus included +reflections and half-turns, but not quarter-turns. They may obviously +be interchanged. So that the correct answer is 2 × 576 = 1,152, counting +reflections and reversals as different. Put in another manner, the +pairs in the top row may be written in 16 × 9 ×4 × 1 = 576 different ways, +and the square then completed in 2 ways, making 1,152 ways in all.</p> + +<hr style="width: 30%;" /> +<p><a name="X_305_THE_THIRTY_SIX_LETTER_BLOCKSa" id="X_305_THE_THIRTY_SIX_LETTER_BLOCKSa"></a><a href="#X_305_THE_THIRTY_SIX_LETTER_BLOCKS"><b>305.—THE THIRTY-SIX LETTER BLOCKS.—<i>solution</i></b></a></p> + +<p>I pointed out that it was impossible to get all the letters into the +box under the conditions, but the puzzle was to place as many as +possible.</p> + +<p><span class='pagenum'>Pg 217<a name="Page_217" id="Page_217"></a></span>This requires a little judgment and careful investigation, or we are +liable to jump to the hasty conclusion that the proper way to solve +the puzzle must be first to place all six of one letter, then all six +of another letter, and so on. As there is only one scheme (with its +reversals) for placing six similar letters so that no two shall be in +a line in any direction, the reader will find that after he has placed +four different kinds of letters, six times each, every place is +occupied except those twelve that form the two long diagonals. He is, +therefore, unable to place more than two each of his last two letters, +and there are eight blanks left. I give such an arrangement in Diagram +1.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a305.png" width="400" height="214" alt="" title="" /> +</div> + +<p>The secret, however, consists in not trying thus to place all six of +each letter. It will be found that if we content ourselves with +placing only five of each letter, this number (thirty in all) may be +got into the box, and there will be only six blanks. But the correct +solution is to place six of each of two letters and five of each of +the remaining four. An examination of Diagram 2 will show that there +are six each of C and D, and five each of A, B, E, and F. There are, +therefore, only four blanks left, and no letter is in line with a +similar letter in any direction.</p> + +<hr style="width: 30%;" /> +<p><a name="X_306_THE_CROWDED_CHESSBOARDa" id="X_306_THE_CROWDED_CHESSBOARDa"></a><a href="#X_306_THE_CROWDED_CHESSBOARD"><b>306.—THE CROWDED CHESSBOARD.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a306.png" width="400" height="398" alt="" title="" /> +</div> + +<p>Here is the solution. Only 8 queens or 8 rooks can be placed on the +board without attack, while the greatest number of bishops is 14, and +of knights 32. But as all these knights must be placed on squares of +the same colour, while the queens occupy four of each colour and the +bishops 7 of each colour, it follows that only 21 knights can be +placed on the same colour in this puzzle. More than 21 knights can be +placed alone on the board if we use both colours, but I have not +succeeded in placing more than 21 on the "crowded chessboard." I +believe the above solution contains the maximum number of pieces, but +possibly some ingenious reader may succeed in getting in another +knight.</p> + +<hr style="width: 30%;" /> +<p><a name="X_307_THE_COLOURED_COUNTERSa" id="X_307_THE_COLOURED_COUNTERSa"></a><a href="#X_307_THE_COLOURED_COUNTERS"><b>307.—THE COLOURED COUNTERS.—<i>solution</i></b></a></p> + +<p>The counters may be arranged in this order:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>R1,</td><td align='center'>B2,</td><td align='center'>Y3,</td><td align='center'>O4,</td><td align='center'>GS.</td></tr> +<tr><td align='center'>Y4,</td><td align='center'>O5,</td><td align='center'>G1,</td><td align='center'>R2,</td><td align='center'>B3.</td></tr> +<tr><td align='center'>G2,</td><td align='center'>R3,</td><td align='center'>B4,</td><td align='center'>Y5,</td><td align='center'>O1.</td></tr> +<tr><td align='center'>B5,</td><td align='center'>Y1,</td><td align='center'>O2,</td><td align='center'>G3,</td><td align='center'>R4.</td></tr> +<tr><td align='center'>O3,</td><td align='center'>G4,</td><td align='center'>R5,</td><td align='center'>B1,</td><td align='center'>Y2.</td></tr> +</table></div> + +<hr style="width: 30%;" /> +<p><a name="X_308_THE_GENTLE_ART_OF_STAMP-LICKINGa" id="X_308_THE_GENTLE_ART_OF_STAMP-LICKINGa"></a><a href="#X_308_THE_GENTLE_ART_OF_STAMP-LICKING"><b>308.—THE GENTLE ART OF STAMP-LICKING.—<i>solution</i></b></a></p> + +<p>The following arrangement shows how sixteen stamps may be stuck on the +card, under the conditions, of a total value of fifty pence, or 4<i>s</i>. +2<i>d</i>.:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a308.png" width="400" height="322" alt="" title="" /> +</div> + +<p>If, after placing the four 5<i>d</i>. stamps, the reader is tempted to place +four 4<i>d</i>. stamps also, he can afterwards only place two of each of the +three other denominations, thus losing two spaces and counting no more +than forty-eight pence, or 4<i>s</i>. This is the pitfall that was hinted at. +(Compare with No. 43, <i>Canterbury Puzzles</i>.)</p> + +<hr style="width: 30%;" /> +<p><a name="X_309_THE_FORTY-NINE_COUNTERSa" id="X_309_THE_FORTY-NINE_COUNTERSa"></a><a href="#X_309_THE_FORTY-NINE_COUNTERS"><b>309.—THE FORTY-NINE COUNTERS.—<i>solution</i></b></a></p> + +<p>The counters may be arranged in this order:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>A1,</td><td align='center'>B2,</td><td align='center'>C3,</td><td align='center'>D4,</td><td align='center'>E5,</td><td align='center'>F6,</td><td align='center'>G7.</td></tr> +<tr><td align='center'>F4,</td><td align='center'>G5,</td><td align='center'>A6,</td><td align='center'>B7,</td><td align='center'>C1,</td><td align='center'>D2,</td><td align='center'>E3.</td></tr> +<tr><td align='center'>D7,</td><td align='center'>E1,</td><td align='center'>F2,</td><td align='center'>G3,</td><td align='center'>A4,</td><td align='center'>B5,</td><td align='center'>C6.</td></tr> +<tr><td align='center'>B3,</td><td align='center'>C4,</td><td align='center'>D5,</td><td align='center'>E6,</td><td align='center'>F7,</td><td align='center'>G1,</td><td align='center'>A2.</td></tr> +<tr><td align='center'>G6,</td><td align='center'>A7,</td><td align='center'>B1,</td><td align='center'>C2,</td><td align='center'>D3,</td><td align='center'>E4,</td><td align='center'>F5.</td></tr> +<tr><td align='center'>E2,</td><td align='center'>F3,</td><td align='center'>G4,</td><td align='center'>A5,</td><td align='center'>B6,</td><td align='center'>C7,</td><td align='center'>D1.</td></tr> +<tr><td align='center'>C5,</td><td align='center'>D6,</td><td align='center'>E7,</td><td align='center'>F1,</td><td align='center'>G2,</td><td align='center'>A3,</td><td align='center'>B4.</td></tr> +</table></div> + +<hr style="width: 30%;" /> +<p><a name="X_310_THE_THREE_SHEEPa" id="X_310_THE_THREE_SHEEPa"></a><a href="#X_310_THE_THREE_SHEEP"><b>310.—THE THREE SHEEP.—<i>solution</i></b></a></p> + +<p>The number of different ways in which the three sheep may be placed so +that every pen <span class='pagenum'>Pg 218<a name="Page_218" id="Page_218"></a></span>shall always be either occupied or in line with at +least one sheep is forty-seven.</p> + +<p>The following table, if used with the key in Diagram 1, will enable +the reader to place them in all these ways:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' class='bb br'>Two Sheep.</td><td align='center' class='bb br'>Third Sheep.</td><td align='center' class='bb'>No. of <br />Ways.</td></tr> +<tr><td align='center' class='br'>A and B</td><td align='left' class='br'>C, E, G, K, L, N, or P</td><td align='center'>7</td></tr> +<tr><td align='center' class='br'>A and C</td><td align='left' class='br'>I, J, K, or O</td><td align='center'>4</td></tr> +<tr><td align='center' class='br'>A and D</td><td align='left' class='br'>M, N, or J</td><td align='center'>3</td></tr> +<tr><td align='center' class='br'>A and F</td><td align='left' class='br'>J, K, L, or P</td><td align='center'>4</td></tr> +<tr><td align='center' class='br'>A and G</td><td align='left' class='br'>H, J, K, N, O, or P</td><td align='center'>6</td></tr> +<tr><td align='center' class='br'>A and H</td><td align='left' class='br'>K, L, N, or O</td><td align='center'>4</td></tr> +<tr><td align='center' class='br'>A and O</td><td align='left' class='br'>K or L</td><td align='center'>2</td></tr> +<tr><td align='center' class='br'>B and C</td><td align='left' class='br'>N</td><td align='center'>1</td></tr> +<tr><td align='center' class='br'>B and E</td><td align='left' class='br'>F, H, K, or L</td><td align='center'>4</td></tr> +<tr><td align='center' class='br'>B and F</td><td align='left' class='br'>G, J, N, or O</td><td align='center'>4</td></tr> +<tr><td align='center' class='br'>B and G</td><td align='left' class='br'>K, L, or N</td><td align='center'>3</td></tr> +<tr><td align='center' class='br'>B and H</td><td align='left' class='br'>J or N</td><td align='center'>2</td></tr> +<tr><td align='center' class='br'>B and J</td><td align='left' class='br'>K or L</td><td align='center'>2</td></tr> +<tr><td align='center' class='br'>F and G</td><td align='left' class='br'>J</td><td align='center'>1</td></tr> +<tr><td align='center' class='br'></td><td align='left' class='br'></td><td align='center' class='bt'>47</td></tr> +</table></div> + +<p>This, of course, means that if you place sheep in the pens marked A +and B, then there are seven different pens in which you may place the +third sheep, giving seven different solutions. It was understood that +reversals and reflections do not count as different.</p> + +<p>If one pen at least is to be <i>not</i> in line with a sheep, there would +be thirty solutions to that problem. If we counted all the reversals +and reflections of these 47 and 30 cases respectively as different, +their total would be 560, which is the number of different ways in +which the sheep may be placed in three pens without any conditions. I +will remark that there are three ways in which two sheep may be placed +so that every pen is occupied or in line, as in Diagrams 2, 3, and 4, +but in every case each sheep is in line with its companion. There are +only two ways in which three sheep may be so placed that every pen +shall be occupied or in line, but no sheep in line with another. These +I show in Diagrams 5 and 6. Finally, there is only one way in which +three sheep may be placed so that at least one pen shall not be in +line with a sheep and yet no sheep in line with another. Place the +sheep in C, E, L. This is practically all there is to be said on this +pleasant pastoral subject.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a310.png" width="600" height="449" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_311_THE_FIVE_DOGS_PUZZLEa" id="X_311_THE_FIVE_DOGS_PUZZLEa"></a><a href="#X_311_THE_FIVE_DOGS_PUZZLE"><b>311.—THE FIVE DOGS PUZZLE.—<i>solution</i></b></a></p> + +<p>The diagrams show four fundamentally different solutions. In the case +of A we can reverse <span class='pagenum'>Pg 219<a name="Page_219" id="Page_219"></a></span>the order, so that the single dog is in the +bottom row and the other four shifted up two squares. Also we may use +the next column to the right and both of the two central horizontal +rows. Thus A gives 8 solutions. Then B may be reversed and placed in +either diagonal, giving 4 solutions. Similarly C will give 4 +solutions. The line in D being symmetrical, its reversal will not be +different, but it may be disposed in 4 different directions. We thus +have in all 20 different solutions.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a311.png" width="400" height="418" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_312_THE_FIVE_CRESCENTS_OF_BYZANTIUMa" id="X_312_THE_FIVE_CRESCENTS_OF_BYZANTIUMa"></a><a href="#X_312_THE_FIVE_CRESCENTS_OF_BYZANTIUM"><b>312.—THE FIVE CRESCENTS OF BYZANTIUM.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/a312.png" width="300" height="300" alt="" title="" /> +</div> + +<p>If that ancient architect had arranged his five crescent tiles in the +manner shown in the following diagram, every tile would have been +watched over by, or in a line with, at least one crescent, and space +would have been reserved for a perfectly square carpet equal in area +to exactly half of the pavement. It is a very curious fact that, +although there are two or three solutions allowing a carpet to be laid +down within the conditions so as to cover an area of nearly +twenty-nine of the tiles, this is the only possible solution giving +exactly half the area of the pavement, which is the largest space +obtainable.</p> + +<hr style="width: 30%;" /> +<p><a name="X_313_QUEENS_AND_BISHOP_PUZZLEa" id="X_313_QUEENS_AND_BISHOP_PUZZLEa"></a><a href="#X_313_QUEENS_AND_BISHOP_PUZZLE"><b>313.—QUEENS AND BISHOP PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a313a.png" width="400" height="396" alt="" title="" /> +</div> + +<p>The bishop is on the square originally occupied by the rook, and the +four queens are so placed that every square is either occupied or +attacked by a piece. (Fig. 1.)</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a313b.png" width="400" height="398" alt="" title="" /> +</div> + +<p>I pointed out in 1899 that if four queens are placed as shown in the +diagram (Fig. 2), then the fifth queen may be placed on any one of the +twelve squares marked a, b, c, d, and e; or a rook on the two squares, +c; or a bishop on the eight squares, a, b, and e; or a pawn on <span class='pagenum'>Pg 220<a name="Page_220" id="Page_220"></a></span>the +square b; or a king on the four squares, b, c, and e. The only known +arrangement for four queens and a knight is that given by Mr. J. +Wallis in <i>The Strand Magazine</i> for August 1908, here reproduced. +(Fig. 3.)</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a313c.png" width="400" height="394" alt="" title="" /> +</div> + +<p>I have recorded a large number of solutions with four queens and a +rook, or bishop, but the only arrangement, I believe, with three +queens and two rooks in which all the pieces are guarded is that of +which I give an illustration (Fig. 4), first published by Dr. C. +Planck. But I have since found the accompanying solution with three +queens, a rook, and a bishop, though the pieces do not protect one +another. (Fig. 5.)</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a313d.png" width="400" height="398" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a313e.png" width="400" height="396" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_314_THE_SOUTHERN_CROSSa" id="X_314_THE_SOUTHERN_CROSSa"></a><a href="#X_314_THE_SOUTHERN_CROSS"><b>314.—THE SOUTHERN CROSS.—<i>solution</i></b></a></p> + +<p>My readers have been so familiarized with the fact that it requires at +least five planets to attack every one of a square arrangement of +sixty-four stars that many of them have, perhaps, got to believe that +a larger square arrangement of stars must need an increase of planets. +It was to correct this possible error of reasoning, and so warn +readers against another of those numerous little pitfalls in the world +of puzzledom, that I devised this new stellar problem. Let me then +state at once that, in the case of a square arrangement of eighty one +stars, there are several ways of placing five planets so that every +star shall be in line with at least one planet vertically, +horizontally, or diagonally. Here is the solution to the "Southern +Cross": —</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a314.png" width="400" height="400" alt="" title="" /> +</div> + +<p><span class='pagenum'>Pg 221<a name="Page_221" id="Page_221"></a></span>It will be remembered that I said that the five planets in their new +positions "will, of course, obscure five other stars in place of those +at present covered." This was to exclude an easier solution in which +only four planets need be moved.</p> + +<hr style="width: 30%;" /> +<p><a name="X_315_THE_HAT-PEG_PUZZLEa" id="X_315_THE_HAT-PEG_PUZZLEa"></a><a href="#X_315_THE_HAT-PEG_PUZZLE"><b>315.—THE HAT-PEG PUZZLE.—<i>solution</i></b></a></p> + +<p>The moves will be made quite clear by a reference to the diagrams, +which show the position on the board after each of the four moves. The +darts indicate the successive removals that have been made. It will be +seen that at every stage all the squares are either attacked or +occupied, and that after the fourth move no queen attacks any other. +In the case of the last move the queen in the top row might also have +been moved one square farther to the left. This is, I believe, the +only solution to the puzzle.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a315.png" width="600" height="634" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_316_THE_AMAZONSa" id="X_316_THE_AMAZONSa"></a><a href="#X_316_THE_AMAZONS"><b>316.—THE AMAZONS.—<i>solution</i></b></a></p> + +<p>It will be seen that only three queens have been removed from their +positions on the edge of the board, and that, as a consequence, eleven +squares (indicated by the black dots) are left unattacked by any +queen. I will hazard the statement that eight queens cannot be placed +on the chessboard so as to leave more than eleven squares unattacked. +It is true that we have no rigid proof of this yet, but I have +<span class='pagenum'>Pg 222<a name="Page_222" id="Page_222"></a></span>entirely convinced myself of the truth of the statement. There are at +least five different ways of arranging the queens so as to leave +eleven squares unattacked.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a316.png" width="400" height="411" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_317_A_PUZZLE_WITH_PAWNSa" id="X_317_A_PUZZLE_WITH_PAWNSa"></a><a href="#X_317_A_PUZZLE_WITH_PAWNS"><b>317.—A PUZZLE WITH PAWNS.—<i>solution</i></b></a></p> + +<p>Sixteen pawns may be placed so that no three shall be in a straight +line in any possible direction, as in the diagram. We regard, as the +conditions required, the pawns as mere points on a plane.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a317.png" width="400" height="396" alt="" title="" /> +</div> +<hr style="width: 30%;" /> +<p><a name="X_318_LION-HUNTINGa" id="X_318_LION-HUNTINGa"></a><a href="#X_318_LION-HUNTING"><b>318.—LION-HUNTING.—<i>solution</i></b></a></p> + +<p>There are 6,480 ways of placing the man and the lion, if there are no +restrictions whatever except that they must be on different spots. +This is obvious, because the man may be placed on any one of the 81 +spots, and in every case there are 80 spots remaining for the lion; +therefore 81 × 80 = 6,480. Now, if we deduct the number of ways in +which the lion and the man may be placed on the same path, the result +must be the number of ways in which they will not be on the same path. +The number of ways in which they may be in line is found without much +difficulty to be 816. Consequently, 6,480 - 816 = 5,664, the required +answer.</p> + +<p>The general solution is this: <sup>1</sup>/<sub>3</sub>n(n - 1) (3n<sup>2</sup> - n + 2). This is, of +course, equivalent to saying that if we call the number of squares on +the side of a "chessboard" <i>n</i>, then the formula shows the number of +ways in which two bishops may be placed without attacking one another. +Only in this case we must divide by two, because the two bishops have +no distinct individuality, and cannot produce a different solution by +mere exchange of places.</p> + +<hr style="width: 30%;" /> +<p><a name="X_319_THE_KNIGHT-GUARDSa" id="X_319_THE_KNIGHT-GUARDSa"></a><a href="#X_319_THE_KNIGHT-GUARDS"><b>319.—THE KNIGHT-GUARDS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a319a.png" width="400" height="406" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a319b.png" width="400" height="420" alt="" title="" /> +</div> + +<p>The smallest possible number of knights with which this puzzle can be +solved is fourteen.</p> + +<p><span class='pagenum'>Pg 223<a name="Page_223" id="Page_223"></a></span>It has sometimes been assumed that there are a great many different +solutions. As a matter of fact, there are only three arrangements—not +counting mere reversals and reflections as different. Curiously +enough, nobody seems ever to have hit on the following simple proof, +or to have thought of dealing with the black and the white squares +separately.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a319c.png" width="400" height="429" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a319d.png" width="400" height="427" alt="" title="" /> +</div> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a319e.png" width="400" height="430" alt="" title="" /> +</div> + +<p>Seven knights can be placed on the board on white squares so as to +attack every black square in two ways only. These are shown in +Diagrams 1 and 2. Note that three knights occupy the same position in +both arrangements. It is therefore clear that if we turn the board so +that a black square shall be in the top left-hand corner instead of a +white, and place the knights in exactly the same positions, we shall +have two similar ways of attacking all the white squares. I will +assume the reader has made the two last described diagrams on +transparent paper, and marked them <i>1a</i> and <i>2a</i>. Now, by placing the +transparent Diagram <i>1a</i> over 1 you will be able to obtain the +solution in Diagram 3, by placing <i>2a</i> over 2 you will get Diagram 4, +and by placing <i>2a</i> over 1 you will get Diagram 5. You may now try all +possible combinations of those two pairs of diagrams, but you will +only get the three arrangements I have given, or their reversals and +reflections. Therefore these three solutions are all that exist.</p> + +<hr style="width: 30%;" /> +<p><a name="X_320_THE_ROOKS_TOURa" id="X_320_THE_ROOKS_TOURa"></a><a href="#X_320_THE_ROOKS_TOUR"><b>320.—THE ROOK'S TOUR.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a320a.png" width="400" height="398" alt="" title="" /> +</div> + +<p>The only possible minimum solutions are shown in the two diagrams, +where it will be seen that only sixteen moves are required to perform +the feat. Most people find it difficult to reduce the number of moves +below seventeen.</p> + +<p><span class='pagenum'>Pg 224<a name="Page_224" id="Page_224"></a></span></p> +<div class="figcenter" style="width: 400px;"> +<img src="images/a320b.png" width="400" height="396" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_321_THE_ROOKS_JOURNEYa" id="X_321_THE_ROOKS_JOURNEYa"></a><a href="#X_321_THE_ROOKS_JOURNEY"><b>321.—THE ROOK'S JOURNEY.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a321.png" width="400" height="392" alt="" title="" /> +</div> + +<p>I show the route in the diagram. It will be seen that the tenth move +lands us at the square marked "10," and that the last move, the +twenty-first, brings us to a halt on square "21."</p> + +<hr style="width: 30%;" /> +<p><a name="X_322_THE_LANGUISHING_MAIDENa" id="X_322_THE_LANGUISHING_MAIDENa"></a><a href="#X_322_THE_LANGUISHING_MAIDEN"><b>322.—THE LANGUISHING MAIDEN.—<i>solution</i></b></a></p> + +<p>The dotted line shows the route in twenty-two straight paths by which +the knight may rescue the maiden. It is necessary, after entering the +first cell, immediately to return before entering another. Otherwise a +solution would not be possible. (See "<a href="#X_250_THE_GRAND_TOURa">The Grand Tour</a>," <a href="#Page_200">p. 200</a>.)</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a322.png" width="400" height="397" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_323_A_DUNGEON_PUZZLEa" id="X_323_A_DUNGEON_PUZZLEa"></a><a href="#X_323_A_DUNGEON_PUZZLE"><b>323.—A DUNGEON PUZZLE.—<i>solution</i></b></a></p> + +<p>If the prisoner takes the route shown in the diagram—where for +clearness the doorways are omitted—he will succeed in visiting every +cell once, and only once, in as many as fifty-seven straight lines. No +rook's path over the chessboard can exceed this number of moves.</p> + + +<div class="figcenter" style="width: 400px;"> +<img src="images/a323.png" width="400" height="396" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_324_THE_LION_AND_THE_MANa" id="X_324_THE_LION_AND_THE_MANa"></a><a href="#X_324_THE_LION_AND_THE_MAN"><b>324.—THE LION AND THE MAN.—<i>solution</i></b></a></p> + +<p>First of all, the fewest possible straight lines in each case are +twenty-two, and in order that no cell may be visited twice it is +absolutely necessary that each should pass into one cell and then +immediately "visit" the one from which he started, afterwards +proceeding by way of the second available cell. In the following +diagram the man's route is indicated by the unbroken lines, and the +lion's by the dotted lines. It will be found, if the two routes are +followed cell by cell with two pencil points, that the lion and the +man never meet. But there was one little point that ought not to be +overlooked—"they occasionally got glimpses of one another." Now, if +we take one route for the <span class='pagenum'>Pg 225<a name="Page_225" id="Page_225"></a></span>man and merely reverse it for the lion, we +invariably find that, going at the same speed, they never get a +glimpse of one another. But in our diagram it will be found that the +man and the lion are in the cells marked A at the same moment, and may +see one another through the open doorways; while the same happens when +they are in the two cells marked B, the upper letters indicating the +man and the lower the lion. In the first case the lion goes straight +for the man, while the man appears to attempt to get in the rear of +the lion; in the second case it looks suspiciously like running away +from one another!</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a324.png" width="400" height="397" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_325_AN_EPISCOPAL_VISITATIONa" id="X_325_AN_EPISCOPAL_VISITATIONa"></a><a href="#X_325_AN_EPISCOPAL_VISITATION"><b>325.—AN EPISCOPAL VISITATION.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a325.png" width="400" height="401" alt="" title="" /> +</div> + +<p>In the diagram I show how the bishop may be made to visit every one of +his white parishes in seventeen moves. It is obvious that we must +start from one corner square and end at the one that is diagonally +opposite to it. The puzzle cannot be solved in fewer than seventeen +moves.</p> + +<hr style="width: 30%;" /> +<p><a name="X_326_A_NEW_COUNTER_PUZZLEa" id="X_326_A_NEW_COUNTER_PUZZLEa"></a><a href="#X_326_A_NEW_COUNTER_PUZZLE"><b>326.—A NEW COUNTER PUZZLE.—<i>solution</i></b></a></p> + +<p>Play as follows: 2—3, 9—4, 10—7, 3—8, 4—2, 7—5, 8—6, 5—10, +6—9, 2—5, 1—6, 6—4, 5—3, 10—8, 4—7, 3—2, 8—1, 7—10. The +white counters have now changed places with the red ones, in eighteen +moves, without breaking the conditions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_327_A_NEW_BISHOPS_PUZZLEa" id="X_327_A_NEW_BISHOPS_PUZZLEa"></a><a href="#X_327_A_NEW_BISHOPS_PUZZLE"><b>327.—A NEW BISHOP'S PUZZLE.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a327.png" width="400" height="255" alt="" title="" /> +</div> + +<p>Play as follows, using the notation indicated by the numbered squares +in Diagram A:—</p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>White.</td><td align='center'>Black.</td></tr> +<tr><td align='left'>1. 18—15</td><td align='left'>1. 3—6</td></tr> +<tr><td align='left'>2. 17—8</td><td align='left'>2. 4—13</td></tr> +<tr><td align='left'>3. 19—14</td><td align='left'>3. 2—7</td></tr> +<tr><td align='left'>4. 15—5</td><td align='left'>4. 6—16</td></tr> +<tr><td align='left'>5. 8—3</td><td align='left'>5. 13-18</td></tr> +<tr><td align='left'>6. 14—9</td><td align='left'>6. 7—12</td></tr> +<tr><td align='left'>7. 5—10</td><td align='left'>7. 16-11</td></tr> +<tr><td align='left'>8. 9—19</td><td align='left'>8. 12—2</td></tr> +<tr><td align='left'>9. 10—4</td><td align='left'>9. 11-17</td></tr> +<tr><td align='left'>10. 20—10</td><td align='left'>10. 1—11</td></tr> +<tr><td align='left'>11. 3—9</td><td align='left'>11. 18—12</td></tr> +<tr><td align='left'>12. 10—13</td><td align='left'>12. 11—8</td></tr> +<tr><td align='left'>13. 19—16</td><td align='left'>13. 2—5</td></tr> +<tr><td align='left'>14. 16—1</td><td align='left'>14. 5—20</td></tr> +<tr><td align='left'>15. 9—6</td><td align='left'>15. 12—15</td></tr> +<tr><td align='left'>16. 13-7</td><td align='left'>16. 8—14</td></tr> +<tr><td align='left'>17. 6—3</td><td align='left'>17. 15-18</td></tr> +<tr><td align='left'>18. 7—2</td><td align='left'>18. 14—19</td></tr> +</table></div> + +<p>Diagram B shows the position after the ninth move. Bishops at 1 and 20 +have not yet moved, but 2 and 19 have sallied forth and returned. In +the end, 1 and 19, 2 and 20, 3 and 17, and 4 and 18 will have +exchanged places. Note the position after the thirteenth move.</p> +<hr style="width: 30%;" /> +<p><a name="X_328_THE_QUEENS_TOURa" id="X_328_THE_QUEENS_TOURa"></a><a href="#X_328_THE_QUEENS_TOUR"><b>328.—THE QUEEN'S TOUR.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a328.png" width="400" height="398" alt="" title="" /> +</div> + +<p><span class='pagenum'>Pg 226<a name="Page_226" id="Page_226"></a></span>The annexed diagram shows a second way of performing the Queen's +Tour. If you break the line at the point J and erase the shorter +portion of that line, you will have the required path solution for any +J square. If you break the line at I, you will have a non-re-entrant +solution starting from any I square. And if you break the line at G, +you will have a solution for any G square. The Queen's Tour previously +given may be similarly broken at three different places, but I seized +the opportunity of exhibiting a second tour.</p> + +<hr style="width: 30%;" /> +<p><a name="X_329_THE_STAR_PUZZLEa" id="X_329_THE_STAR_PUZZLEa"></a><a href="#X_329_THE_STAR_PUZZLE"><b>329.—THE STAR PUZZLE.—<i>solution</i></b></a></p> + +<p>The illustration explains itself. The stars are all struck out in +fourteen straight strokes, starting and ending at a white star.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a329.png" width="400" height="392" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_330_THE_YACHT_RACEa" id="X_330_THE_YACHT_RACEa"></a><a href="#X_330_THE_YACHT_RACE"><b>330.—THE YACHT RACE.—<i>solution</i></b></a></p> + +<p>The diagram explains itself. The numbers will show the direction of +the lines in their proper order, and it will be seen that the seventh +course ends at the flag-buoy, as stipulated.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a330.png" width="400" height="326" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_331_THE_SCIENTIFIC_SKATERa" id="X_331_THE_SCIENTIFIC_SKATERa"></a><a href="#X_331_THE_SCIENTIFIC_SKATER"><b>331.—THE SCIENTIFIC SKATER.—<i>solution</i></b></a></p> + +<p>In this case we go beyond the boundary of the square. Apart from that, +the moves are all queen moves. There are three or four ways in which +it can be done.</p> + +<p>Here is one way of performing the feat:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a331.png" width="400" height="394" alt="" title="" /> +</div> + +<p>It will be seen that the skater strikes out all the stars in one +continuous journey of fourteen straight lines, returning to the point +from which he started. To follow the skater's course in the diagram it +is necessary always to go as far as we can in a straight line before +turning.</p> + +<hr style="width: 30%;" /> +<p><a name="X_332_THE_FORTY-NINE_STARSa" id="X_332_THE_FORTY-NINE_STARSa"></a><a href="#X_332_THE_FORTY-NINE_STARS"><b>332.—THE FORTY-NINE STARS.—<i>solution</i></b></a></p> + +<p>The illustration shows how all the stars may be struck out in twelve +straight strokes, beginning and ending at a black star.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a332.png" width="400" height="396" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 227<a name="Page_227" id="Page_227"></a></span><a name="X_333_THE_QUEENS_JOURNEYa" id="X_333_THE_QUEENS_JOURNEYa"></a><a href="#X_333_THE_QUEENS_JOURNEY"><b>333.—THE QUEEN'S JOURNEY.—<i>solution</i></b></a></p> + +<p>The correct solution to this puzzle is shown in the diagram by the +dark line. The five moves indicated will take the queen the greatest +distance that it is possible for her to go in five moves, within the +conditions. The dotted line shows the route that most people suggest, +but it is not quite so long as the other. Let us assume that the +distance from the centre of any square to the centre of the next in +the same horizontal or vertical line is 2 inches, and that the queen +travels from the centre of her original square to the centre of the +one at which she rests. Then the first route will be found to exceed +67.9 inches, while the dotted route is less than 67.8 inches. The +difference is small, but it is sufficient to settle the point as to +the longer route. All other routes are shorter still than these two.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a333.png" width="400" height="400" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_334_ST_GEORGE_AND_THE_DRAGONa" id="X_334_ST_GEORGE_AND_THE_DRAGONa"></a><a href="#X_334_ST_GEORGE_AND_THE_DRAGON"><b>334.—ST. GEORGE AND THE DRAGON.—<i>solution</i></b></a></p> + +<p>We select for the solution of this puzzle one of the prettiest designs +that can be formed by representing the moves of the knight by lines +from square to square. The chequering of the squares is omitted to +give greater clearness. St. George thus slays the Dragon in strict +accordance with the conditions and in the elegant manner we should +expect of him.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a334.png" width="400" height="403" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_335_FARMER_LAWRENCES_CORNFIELDSa" id="X_335_FARMER_LAWRENCES_CORNFIELDSa"></a><a href="#X_335_FARMER_LAWRENCES_CORNFIELDS"><b>335.—FARMER LAWRENCE'S CORNFIELDS.—<i>solution</i></b></a></p> + +<p>There are numerous solutions to this little agricultural problem. The +version I give in the next column is rather curious on account of the +long parallel straight lines formed by some of the moves.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a335.png" width="400" height="406" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_336_THE_GREYHOUND_PUZZLEa" id="X_336_THE_GREYHOUND_PUZZLEa"></a><a href="#X_336_THE_GREYHOUND_PUZZLE"><b>336.—THE GREYHOUND PUZZLE.—<i>solution</i></b></a></p> + +<p>There are several interesting points involved in this question. In the +first place, if we had made no stipulation as to the positions of the +two ends of the string, it is quite impossible to form any such string +unless we begin and end in the top and bottom row of kennels. We may +begin in the top row and end in the bottom (or, of course, the +reverse), or we may begin in one of these rows and end in the same. +But we can never begin or end in one of the two central rows. Our +places of starting and ending, however, were fixed for us. Yet the +first half of our route must be confined entirely to those squares +that are distinguished in the following diagram by circles, and the +second half will therefore be confined to the squares that are not +circled. The squares reserved for the two half-strings will be seen to +be symmetrical and similar.</p> + +<p>The next point is that the first half-string must end in one of the +central rows, and the <span class='pagenum'>Pg 228<a name="Page_228" id="Page_228"></a></span>second half-string must begin in one of these +rows. This is now obvious, because they have to link together to form +the complete string, and every square on an outside row is connected +by a knight's move with similar squares only—that is, circled or +non-circled as the case may be. The half-strings can, therefore, only +be linked in the two central rows.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a336.png" width="400" height="337" alt="" title="" /> +</div> + +<p>Now, there are just eight different first half-strings, and +consequently also eight second half-strings. We shall see that these +combine to form twelve complete strings, which is the total number +that exist and the correct solution of our puzzle. I do not propose to +give all the routes at length, but I will so far indicate them that if +the reader has dropped any he will be able to discover which they are +and work them out for himself without any difficulty. The following +numbers apply to those in the above diagram.</p> + +<p>The eight first half-strings are: 1 to 6 (2 routes); 1 to 8 (1 route); +1 to 10 (3 routes); 1 to 12 (1 route); and 1 to 14 (1 route). The +eight second half-strings are: 7 to 20 (1 route); 9 to 20 (1 route); +11 to 20 (3 routes); 13 to 20 (1 route); and 15 to 20 (2 routes). +Every different way in which you can link one half-string to another +gives a different solution. These linkings will be found to be as +follows: 6 to 13 (2 cases); 10 to 13 (3 cases); 8 to 11 (3 cases); 8 +to 15 (2 cases); 12 to 9 (1 case); and 14 to 7 (1 case). There are, +therefore, twelve different linkings and twelve different answers to +the puzzle. The route given in the illustration with the greyhound +will be found to consist of one of the three half-strings 1 to 10, +linked to the half-string 13 to 20. It should be noted that ten of the +solutions are produced by five distinctive routes and their +reversals—that is, if you indicate these five routes by lines and +then turn the diagrams upside down you will get the five other routes. +The remaining two solutions are symmetrical (these are the cases where +12 to 9 and 14 to 7 are the links), and consequently they do not +produce new solutions by reversal.</p> + +<hr style="width: 30%;" /> +<p><a name="X_337_THE_FOUR_KANGAROOSa" id="X_337_THE_FOUR_KANGAROOSa"></a><a href="#X_337_THE_FOUR_KANGAROOS"><b>337.—THE FOUR KANGAROOS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a337.png" width="400" height="394" alt="" title="" /> +</div> + +<p>A pretty symmetrical solution to this puzzle is shown in the diagram. +Each of the four kangaroos makes his little excursion and returns to +his corner, without ever entering a square that has been visited by +another kangaroo and without crossing the central line. It will at +once occur to the reader, as a possible improvement of the puzzle, to +divide the board by a central vertical line and make the condition +that this also shall not be crossed. This would mean that each +kangaroo had to confine himself to a square 4 by 4, but it would be +quite impossible, as I shall explain in the next two puzzles.</p> + +<hr style="width: 30%;" /> +<p><a name="X_338_THE_BOARD_IN_COMPARTMENTSa" id="X_338_THE_BOARD_IN_COMPARTMENTSa"></a><a href="#X_338_THE_BOARD_IN_COMPARTMENTS"><b>338.—THE BOARD IN COMPARTMENTS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a338.png" width="400" height="400" alt="" title="" /> +</div> + +<p>In attempting to solve this problem it is first necessary to take the +two distinctive compartments of twenty and twelve squares respectively +and analyse them with a view to deter<span class='pagenum'>Pg 229<a name="Page_229" id="Page_229"></a></span>mining where the necessary +points of entry and exit lie. In the case of the larger compartment it +will be found that to complete a tour of it we must begin and end on +two of the outside squares on the long sides. But though you may start +at any one of these ten squares, you are restricted as to those at +which you can end, or (which is the same thing) you may end at +whichever of these you like, provided you begin your tour at certain +particular squares. In the case of the smaller compartment you are +compelled to begin and end at one of the six squares lying at the two +narrow ends of the compartments, but similar restrictions apply as in +the other instance. A very little thought will show that in the case +of the two small compartments you must begin and finish at the ends +that lie together, and it then follows that the tours in the larger +compartments must also start and end on the contiguous sides.</p> + +<p>In the diagram given of one of the possible solutions it will be seen +that there are eight places at which we may start this particular +tour; but there is only one route in each case, because we must +complete the compartment in which we find ourself before passing into +another. In any solution we shall find that the squares distinguished +by stars must be entering or exit points, but the law of reversals +leaves us the option of making the other connections either at the +diamonds or at the circles. In the solution worked out the diamonds +are used, but other variations occur in which the circle squares are +employed instead. I think these remarks explain all the essential +points in the puzzle, which is distinctly instructive and interesting.</p> + +<hr style="width: 30%;" /> +<p><a name="X_339_THE_FOUR_KNIGHTS_TOURSa" id="X_339_THE_FOUR_KNIGHTS_TOURSa"></a><a href="#X_339_THE_FOUR_KNIGHTS_TOURS"><b>339.—THE FOUR KNIGHTS' TOURS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a339.png" width="400" height="396" alt="" title="" /> +</div> + +<p>It will be seen in the illustration how a chessboard may be divided +into four parts, each of the same size and shape, so that a complete +re-entrant knight's tour may be made on each portion. There is only +one possible route for each knight and its reversal.</p> + +<hr style="width: 30%;" /> +<p><a name="X_340_THE_CUBIC_KNIGHTS_TOURa" id="X_340_THE_CUBIC_KNIGHTS_TOURa"></a><a href="#X_340_THE_CUBIC_KNIGHTS_TOUR"><b>340.—THE CUBIC KNIGHT'S TOUR.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a340.png" width="400" height="515" alt="" title="" /> +</div> + +<p>If the reader should cut out the above diagram, fold it in the form of +a cube, and stick it together by the strips left for that purpose at +the edges, he would have an interesting little curiosity. Or he can +make one on a larger scale for himself. It will be found that if we +imagine the cube to have a complete chessboard on each of its sides, +we may start with the knight on any one of the 384 squares, and make a +complete tour of the cube, always returning to the starting-point. The +method of passing from one side of the cube to another is easily +understood, but, of course, the difficulty consisted in finding the +proper points of entry and exit on each board, the order in which the +different boards should be taken, and in getting arrangements that +would comply with the required conditions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_341_THE_FOUR_FROGSa" id="X_341_THE_FOUR_FROGSa"></a><a href="#X_341_THE_FOUR_FROGS"><b>341.—THE FOUR FROGS.—<i>solution</i></b></a></p> + +<p>The fewest possible moves, counting every move separately, are +sixteen. But the puzzle may be solved in seven plays, as follows, if +any number of successive moves by one frog count as a single play. All +the moves contained within a bracket are a single play; the numbers +refer to the toadstools: (1—5), (3—7, 7—1), (8—4, 4—3, 3—7), +(6—2, 2—8, 8—4, 4—3), (5—6, 6—2, 2—8), (1—5, 5—6), (7—1).</p> + +<p>This is the familiar old puzzle by Guarini, propounded in 1512, and I +give it here in order to explain my "buttons and string" method of +solving this class of moving-counter problem.</p> + +<p><span class='pagenum'>Pg 230<a name="Page_230" id="Page_230"></a></span>Diagram A shows the old way of presenting Guarini's puzzle, the point +being to make the white knights change places with the black ones. In +"The Four Frogs" presentation of the idea the possible directions of +the moves are indicated by lines, to obviate the necessity of the +reader's understanding the nature of the knight's move in chess. But +it will at once be seen that the two problems are identical. The +central square can, of course, be ignored, since no knight can ever +enter it. Now, regard the toadstools as buttons and the connecting +lines as strings, as in Diagram B. Then by disentangling these strings +we can clearly present the diagram in the form shown in Diagram C, +where the relationship between the buttons is precisely the same as in +B. Any solution on C will be applicable to B, and to A. Place your +white knights on 1 and 3 and your black knights on 6 and 8 in the C +diagram, and the simplicity of the solution will be very evident. You +have simply to move the knights round the circle in one direction or +the other. Play over the moves given above, and you will find that +every little difficulty has disappeared.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/a341.png" width="600" height="357" alt="" title="" /> +</div> + +<p>In Diagram D I give another familiar puzzle that first appeared in a +book published in Brussels in 1789, <i>Les Petites Aventures de Jerome +Sharp</i>. Place seven counters on seven of the eight points in the +following manner. You must always touch a point that is vacant with a +counter, and then move it along a straight line leading from that +point to the next vacant point (in either direction), where you +deposit the counter. You proceed in the same way until all the +counters are placed. Remember you always touch a vacant place and +slide the counter from it to the next place, which must be also +vacant. Now, by the "buttons and string" method of simplification we +can transform the diagram into E. Then the solution becomes obvious. +"Always move <i>to</i> the point that you last moved <i>from</i>." This is not, +of course, the only way of placing the counters, but it is the +simplest solution to carry in the mind.</p> + +<p>There are several puzzles in this book that the reader will find lend +themselves readily to this method.</p> + +<hr style="width: 30%;" /> +<p><a name="X_342_THE_MANDARINS_PUZZLEa" id="X_342_THE_MANDARINS_PUZZLEa"></a><a href="#X_342_THE_MANDARINS_PUZZLE"><b>342.—THE MANDARIN'S PUZZLE.—<i>solution</i></b></a></p> + +<p>The rather perplexing point that the solver has to decide for himself +in attacking this puzzle is whether the shaded numbers (those that are +shown in their right places) are mere dummies or not. Ninety-nine +persons out of a hundred might form the opinion that there can be no +advantage in moving any of them, but if so they would be wrong.</p> + +<p>The shortest solution without moving any shaded number is in +thirty-two moves. But the puzzle can be solved in thirty moves. The +trick lies in moving the 6, or the 15, on the second move and +replacing it on the nineteenth move. Here is the solution: +2, 6, 13, 4, 1, 21, 4, 1, 10, 2, 21, 10, 2, 5, 22, 16, 1, 13, 6, 19, 11, 2, 5, 22, 16, 5, 13, 4, 10, 21. +Thirty moves.</p> + +<hr style="width: 30%;" /> +<p><a name="X_343_EXERCISE_FOR_PRISONERSa" id="X_343_EXERCISE_FOR_PRISONERSa"></a><a href="#X_343_EXERCISE_FOR_PRISONERS"><b>343.—EXERCISE FOR PRISONERS.—<i>solution</i></b></a></p> + +<p>There are eighty different arrangements of the numbers in the form of +a perfect knight's path, but only forty of these can be reached +without two men ever being in a cell at the same time. Two is the +greatest number of men that can be given a complete rest, and though +the <span class='pagenum'>Pg 231<a name="Page_231" id="Page_231"></a></span>knight's path can be arranged so as to leave either 7 and 13, 8 +and 13, 5 and 7, or 5 and 13 in their original positions, the +following four arrangements, in which 7 and 13 are unmoved, are the +only ones that can be reached under the moving conditions. It +therefore resolves itself into finding the fewest possible moves that +will lead up to one of these positions. This is certainly no easy +matter, and no rigid rules can be laid down for arriving at the +correct answer. It is largely a matter for individual judgment, +patient experiment, and a sharp eye for revolutions and position.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a343.png" width="400" height="445" alt="" title="" /> +</div> + +<p>As a matter of fact, the position C can be reached in as few as +sixty-six moves in the following manner: 12, 11, 15, 12, 11, 8, 4, 3, +2, 6, 5, 1, 6, 5, 10, 15, 8, 4, 3, 2, 5, 10, 15, 8, 4, 3, 2, 5, 10, +15, 8, 4, 12, 11, 3, 2, 5, 10, 15, 6, 1, 8, 4, 9, 8, 1, 6, 4, 9, 12, +2, 5, 10, 15, 4, 9, 12, 2, 5, 3, 11, 14, 2, 5, 14, 11 = 66 moves. +Though this is the shortest that I know of, and I do not think it can +be beaten, I cannot state positively that there is not a shorter way +yet to be discovered. The most tempting arrangement is certainly A; +but things are not what they seem, and C is really the easiest to +reach.</p> + +<p>If the bottom left-hand corner cell might be left vacant, the +following is a solution in forty-five moves by Mr. R. Elrick: 15, 11, +10, 9, 13, 14, 11, 10, 7, 8, 4, 3, 8, 6, 9, 7, 12, 4, 6, 9, 5, 13, 7, +5, 13, 1, 2, 13, 5, 7, 1, 2, 13, 8, 3, 6, 9, 12, 7, 11, 14, 1, 11, 14, +1. But every man has moved.</p> + +<hr style="width: 30%;" /> +<p><a name="X_344_THE_KENNEL_PUZZLEa" id="X_344_THE_KENNEL_PUZZLEa"></a><a href="#X_344_THE_KENNEL_PUZZLE"><b>344.—THE KENNEL PUZZLE.—<i>solution</i></b></a></p> + +<p>The first point is to make a choice of the most promising knight's +string and then consider the question of reaching the arrangement in +the fewest moves. I am strongly of opinion that the best string is the +one represented in the following diagram, in which it will be seen +that each successive number is a knight's move from the preceding one, +and that five of the dogs (1, 5, 10, 15, and 20) never leave their +original kennels.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a344.png" width="400" height="402" alt="" title="" /> +</div> + +<p>This position may be arrived at in as few as forty-six moves, as +follows: 16—21, 16—22, 16—23, 17—16, 12—17, 12—22, 12—21,7—12, +7—17, 7—22, 11—12, 11—17, 2—7, 2—12, 6—11, 8—7, 8—6, 13—8, +18—13, 11—18, 2—17, 18—12, 18—7, 18—2, 13—7, 3—8, 3—13, 4—3, +4—8, 9—4, 9—3, 14—9, 14—4, 19—14, 19—9, 3—14, 3—19, 6—12, +6—13, 6—14, 17—11, 12—16, 2—12, 7—17, 11—13, 16—18 = 46 moves. +I am, of course, not able to say positively that a solution cannot be +discovered in fewer moves, but I believe it will be found a very hard +task to reduce the number.</p> + +<hr style="width: 30%;" /> +<p><a name="X_345_THE_TWO_PAWNSa" id="X_345_THE_TWO_PAWNSa"></a><a href="#X_345_THE_TWO_PAWNS"><b>345.—THE TWO PAWNS.—<i>solution</i></b></a></p> + +<p>Call one pawn A and the other B. Now, owing to that optional first +move, either pawn may make either 5 or 6 moves in reaching the eighth +square. There are, therefore, four cases to be considered: (1) A 6 +moves and B 6 moves; (2) A 6 moves and B 5 moves; (3) A 5 moves and B +6 moves; (4) A 5 moves and B 5 moves. In case (1) there are 12 moves, +and we may select any 6 of these for A. Therefore 7 × 8 × 9 × 10 × 11 × 12 +divided by 1 × 2 × 3 × 4 × 5 × 6 gives us the number of variations for this +case—that is, 924. Similarly for case (2), 6 selections out of 11 +will be 462; in case (3), 5 selections out of 11 will also be 462; and +in case (4), 5 selections out of 10 will be 252. Add these four +numbers together and we get 2,100, which is the correct number of +different ways in which the pawns may advance under the conditions. +(See No. <a href="#X_270_THE_GLASS_BALLSa">270</a>, on p. <a href="#Page_204">204</a>.)</p> + +<hr style="width: 30%;" /> +<p><a name="X_346_SETTING_THE_BOARDa" id="X_346_SETTING_THE_BOARDa"></a><a href="#X_346_SETTING_THE_BOARD"><b>346.—SETTING THE BOARD.—<i>solution</i></b></a></p> + +<p>The White pawns may be arranged in 40,320 ways, the White rooks in 2 +ways, the bishops in 2 ways, and the knights in 2 ways. Multiply these +numbers together, and we find that the White pieces may be placed in +322,560 different <span class='pagenum'>Pg 232<a name="Page_232" id="Page_232"></a></span>ways. The Black pieces may, of course, be placed in +the same number of ways. Therefore the men may be set up in 322,560 × +322,560 = 104,044,953,600 ways. But the point that nearly everybody +overlooks is that the board may be placed in two different ways for +every arrangement. Therefore the answer is doubled, and is +208,089,907,200 different ways.</p> + +<hr style="width: 30%;" /> +<p><a name="X_347_COUNTING_THE_RECTANGLESa" id="X_347_COUNTING_THE_RECTANGLESa"></a><a href="#X_347_COUNTING_THE_RECTANGLES"><b>347.—COUNTING THE RECTANGLES.—<i>solution</i></b></a></p> + +<p>There are 1,296 different rectangles in all, 204 of which are squares, +counting the square board itself as one, and 1,092 rectangles that are +not squares. The general formula is that a board of <i>n</i><sup>2</sup> squares +contains <span class='su2'>((<i>n</i><sup>2</sup> + <i>n</i>)<sup>2</sup>)</span>/<sub>4</sub> rectangles, of which <span class='su2'>(2<i>n</i><sup>3</sup> + 3<i>n</i><sup>2</sup> + <i>n</i>)</span>/<sub>6</sub> +are squares and <span class='su2'>(3<i>n</i><sup>4</sup> + 2<i>n</i><sup>3</sup> - 3<i>n</i><sup>2</sup> - 2<i>n</i>)</span>/<sub>12</sub> are rectangles that are +not squares. It is curious and interesting that the total number of +rectangles is always the square of the triangular number whose side is +<i>n</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_348_THE_ROOKERYa" id="X_348_THE_ROOKERYa"></a><a href="#X_348_THE_ROOKERY"><b>348.—THE ROOKERY.—<i>solution</i></b></a></p> + +<p>The answer involves the little point that in the final position the +numbered rooks must be in numerical order in the direction contrary to +that in which they appear in the original diagram, otherwise it cannot +be solved. Play the rooks in the following order of their numbers. As +there is never more than one square to which a rook can move (except +on the final move), the notation is obvious—5, 6, 7, 5, 6, 4, 3, 6, +4, 7, 5, 4, 7, 3, 6, 7, 3, 5, 4, 3, 1, 8, 3, 4, 5, 6, 7, 1, 8, 2, 1, +and rook takes bishop, checkmate. These are the fewest possible +moves—thirty-two. The Black king's moves are all forced, and need not +be given.</p> + +<hr style="width: 30%;" /> +<p><a name="X_349_STALEMATEa" id="X_349_STALEMATEa"></a><a href="#X_349_STALEMATE"><b>349.—STALEMATE.—<i>solution</i></b></a></p> + +<p>Working independently, the same position was arrived at by Messrs. S. +Loyd, E.N. Frankenstein, W.H. Thompson, and myself. So the following +may be accepted as the best solution possible to this curious problem +:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>White.</td><td align='center'>Black.</td></tr> +<tr><td align='left'>1. P—Q4</td><td align='left'>1. P—K4</td></tr> +<tr><td align='left'>2. Q—Q3</td><td align='left'>2. Q—R5</td></tr> +<tr><td align='left'>3. Q—KKt3</td><td align='left'>3. B—Kt5 ch</td></tr> +<tr><td align='left'>4. Kt—Q2</td><td align='left'>4. P—QR4</td></tr> +<tr><td align='left'>5. P—R4</td><td align='left'>5. P—Q3</td></tr> +<tr><td align='left'>6. P—R3</td><td align='left'>6. B—K3</td></tr> +<tr><td align='left'>7. R—R3</td><td align='left'>7. P—KB4</td></tr> +<tr><td align='left'>8. Q—R2</td><td align='left'>8. P—B4</td></tr> +<tr><td align='left'>9. R—KKt3</td><td align='left'>9. B—Kt6</td></tr> +<tr><td align='left'>10. P—QB4</td><td align='left'>10. P—B5</td></tr> +<tr><td align='left'>11. P—B3</td><td align='left'>11. P—K5</td></tr> +<tr><td align='left'>12. P—Q5</td><td align='left'>12. P—K6</td></tr> +</table></div> + +<p>And White is stalemated.</p> + +<p>We give a diagram of the curious position arrived at. It will be seen +that not one of White's pieces may be moved.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a349.png" width="400" height="405" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_350_THE_FORSAKEN_KINGa" id="X_350_THE_FORSAKEN_KINGa"></a><a href="#X_350_THE_FORSAKEN_KING"><b>350.—THE FORSAKEN KING.—<i>solution</i></b></a></p> + +<p>Play as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>White.</td><td align='center'>Black.</td></tr> +<tr><td align='left'>1. P to K 4th</td><td align='left'>1. Any move</td></tr> +<tr><td align='left'>2. Q to Kt 4th</td><td align='left'>2. Any move except on KB file (a)</td></tr> +<tr><td align='left'>3. Q to Kt 7th</td><td align='left'>3. K moves to royal row</td></tr> +<tr><td align='left'>4. B to Kt 5th</td><td align='left'>4. Any move</td></tr> +<tr><td align='left'>5. Mate in two moves</td></tr> +<tr><td align='left'></td><td align='left'>If 3. K other than to royal row</td></tr> +<tr><td align='left'>4. P to Q 4th</td><td align='left'>4. Any move</td></tr> +<tr><td align='left'>5. Mate in two moves</td></tr> +<tr><td align='left'></td><td align='left'>(a) If 2. Any move on KB file</td></tr> +<tr><td align='left'>3. Q to Q 7th</td><td align='left'>3. K moves to royal row</td></tr> +<tr><td align='left'>4. P to Q Kt 3rd</td><td align='left'>4. Any move</td></tr> +<tr><td align='left'>5. Mate in two moves</td></tr> +<tr><td align='left'></td><td align='left'>If 3. K other than to royal row</td></tr> +<tr><td align='left'>4. P to Q 4th</td><td align='left'>4. Any move</td></tr> +<tr><td align='left'>5. Mate in two moves</td></tr> +</table></div> + +<p>Of course, by "royal row" is meant the row on which the king +originally stands at the beginning of a game. Though, if Black plays +badly, he may, in certain positions, be mated in fewer moves, the +above provides for every variation he can possibly bring about.</p> + +<hr style="width: 30%;" /> +<p><a name="X_351_THE_CRUSADERa" id="X_351_THE_CRUSADERa"></a><a href="#X_351_THE_CRUSADER"><b>351.—THE CRUSADER.—<i>solution</i></b></a></p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>White.</td><td align='center'>Black.</td></tr> +<tr><td align='left'>1. Kt to QB 3rd</td><td align='left'>1. P to Q 4th</td></tr> +<tr><td align='left'>2. Kt takes QP</td><td align='left'>2. Kt to QB 3rd</td></tr> +<tr><td align='left'>3. Kt takes KP</td><td align='left'>3. P to KKt 4th</td></tr> +<tr><td align='left'>4. Kt takes B</td><td align='left'>4. Kt to KB 3rd</td></tr> +<tr><td align='left'>5. Kt takes P</td><td align='left'>5. Kt to K 5th</td></tr> +<tr><td align='left'>6. Kt takes Kt</td><td align='left'>6. Kt to B 6th</td></tr> +<tr><td align='left'>7. Kt takes Q</td><td align='left'>7. R to KKt sq</td></tr> +<tr><td align='left'>8. Kt takes BP</td><td align='left'>8. R to KKt 3rd</td></tr> +<tr><td align='left'>9. Kt takes P</td><td align='left'>9. R to K 3rd</td></tr> +<tr><td align='left'>10. Kt takes P</td><td align='left'>10. Kt to Kt 8th</td></tr> +<tr><td align='left'>11. Kt takes B</td><td align='left'>11. R to R 6th</td></tr> +<tr><td align='left'>12. Kt takes R</td><td align='left'>12. P to Kt 4th</td></tr> +<tr><td align='left'>13. Kt takes P (ch)</td><td align='left'>13. K to B 2nd</td></tr> +<tr><td align='left'>14. Kt takes P</td><td align='left'>14. K to Kt 3rd</td></tr> +<tr><td align='left'>15. Kt takes R</td><td align='left'>15. K to R 4th</td></tr> +<tr><td align='left'>16. Kt takes Kt</td><td align='left'>16. K to R 5th</td></tr> +<tr><td align='center' colspan='2'>White now mates in three moves.</td></tr> +<tr><td align='left'>17. P to Q 4th</td><td align='left'>17. K to R 4th</td></tr> +<tr><td align='left'>18. Q to Q 3rd</td><td align='left'>18. K moves</td></tr> +<tr><td align='left'>19. Q to KR 3rd (mate)</td></tr> +<tr><td align='left'></td><td align='left'>If 17. K to Kt 5th</td></tr> +<tr><td align='left'>18. P to K 4th (dis. ch)</td><td align='left'>18. K moves</td></tr> +<tr><td align='left'>19. P to KKt 3rd (mate)</td></tr> +</table></div> + +<p><span class='pagenum'>Pg 233<a name="Page_233" id="Page_233"></a></span></p> +<p>The position after the sixteenth move, with the mate in three moves, +was first given by S. Loyd in <i>Chess Nuts</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_352_IMMOVABLE_PAWNSa" id="X_352_IMMOVABLE_PAWNSa"></a><a href="#X_352_IMMOVABLE_PAWNS"><b>352.—IMMOVABLE PAWNS.—<i>solution</i></b></a></p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>1. Kt to KB 3</td></tr> +<tr><td align='left'>2. Kt to KR 4</td></tr> +<tr><td align='left'>3. Kt to Kt 6</td></tr> +<tr><td align='left'>4. Kt takes R</td></tr> +<tr><td align='left'>5. Kt to Kt 6</td></tr> +<tr><td align='left'>6. Kt takes B</td></tr> +<tr><td align='left'>7. K takes Kt</td></tr> +<tr><td align='left'>8. Kt to QB 3</td></tr> +<tr><td align='left'>9. Kt to R 4</td></tr> +<tr><td align='left'>10. Kt to Kt 6</td></tr> +<tr><td align='left'>11. Kt takes R</td></tr> +<tr><td align='left'>12. Kt to Kt 6</td></tr> +<tr><td align='left'>13. Kt takes B</td></tr> +<tr><td align='left'>14. Kt to Q 6</td></tr> +<tr><td align='left'>15. Q to K sq</td></tr> +<tr><td align='left'>16. Kt takes Q</td></tr> +<tr><td align='left'>17. K takes Kt, and the position is reached.</td></tr> +</table></div> + +<p>Black plays precisely the same moves as White, and therefore we give +one set of moves only. The above seventeen moves are the fewest +possible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_353_THIRTY-SIX_MATESa" id="X_353_THIRTY-SIX_MATESa"></a><a href="#X_353_THIRTY-SIX_MATES"><b>353.—THIRTY-SIX MATES.—<i>solution</i></b></a></p> + +<p>Place the remaining eight White pieces thus: K at KB 4th, Q at QKt +6th, R at Q 6th, R at KKt 7th, B at Q 5th, B at KR 8th, Kt at QR 5th, +and Kt at QB 5th. The following mates can then be given:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>By discovery from Q</td><td align='right'>8</td></tr> +<tr><td align='left'>By discovery from R at Q 6th</td><td align='right'>13</td></tr> +<tr><td align='left'>By discovery from B at R 8th</td><td align='right'>11</td></tr> +<tr><td align='left'>Given by Kt at R 5th</td><td align='right'>2</td></tr> +<tr><td align='left'>Given by pawns</td><td align='right'>2</td></tr> +<tr><td align='left'>Total</td><td align='right' class='bt'>36</td></tr> +</table></div> + +<p>Is it possible to construct a position in which more than thirty-six +different mates on the move can be given? So far as I know, nobody has +yet beaten my arrangement.</p> + +<hr style="width: 30%;" /> +<p><a name="X_354_AN_AMAZING_DILEMMAa" id="X_354_AN_AMAZING_DILEMMAa"></a><a href="#X_354_AN_AMAZING_DILEMMA"><b>354.—AN AMAZING DILEMMA.—<i>solution</i></b></a></p> + +<p>Mr Black left his king on his queen's knight's 7th, and no matter what +piece White chooses for his pawn, Black cannot be checkmated. As we +said, the Black king takes no notice of checks and never moves. White +may queen his pawn, capture the Black rook, and bring his three pieces +up to the attack, but mate is quite impossible. The Black king cannot +be left on any other square without a checkmate being possible.</p> + +<p>The late Sam Loyd first pointed out the peculiarity on which this +puzzle is based.</p> + +<hr style="width: 30%;" /> +<p><a name="X_355_CHECKMATEa" id="X_355_CHECKMATEa"></a><a href="#X_355_CHECKMATE"><b>355.—CHECKMATE!—<i>solution</i></b></a></p> + +<p>Remove the White pawn from B 6th to K 4th and place a Black pawn on +Black's KB 2nd. Now, White plays P to K 5th, check, and Black must +play P to B 4th. Then White plays P takes P <i>en passant</i>, checkmate. +This was therefore White's last move, and leaves the position given. +It is the only possible solution.</p> + +<hr style="width: 30%;" /> +<p><a name="X_356_QUEER_CHESSa" id="X_356_QUEER_CHESSa"></a><a href="#X_356_QUEER_CHESS"><b>356.—QUEER CHESS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a356.png" width="400" height="163" alt="" title="" /> +</div> + +<p>If you place the pieces as follows (where only a portion of the board +is given, to save space), the Black king is in check, with no possible +move open to him. The reader will now see why I avoided the term +"checkmate," apart from the fact that there is no White king. The +position is impossible in the game of chess, because Black could not be +given check by both rooks at the same time, nor could he have moved into +check on his last move.</p> + +<p>I believe the position was first published by the late S. Loyd.</p> + +<hr style="width: 30%;" /> +<p><a name="X_357_ANCIENT_CHINESE_PUZZLEa" id="X_357_ANCIENT_CHINESE_PUZZLEa"></a><a href="#X_357_ANCIENT_CHINESE_PUZZLE"><b>357.—ANCIENT CHINESE PUZZLE.—<i>solution</i></b></a></p> + +<p>Play as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>1. R—Q 6</td></tr> +<tr><td align='left'>2. K—R 7</td></tr> +<tr><td align='left'>3. R (R 6)—B 6 (mate).</td></tr> +</table></div> + +<p>Black's moves are forced, so need not be given.</p> + +<hr style="width: 30%;" /> +<p><a name="X_358_THE_SIX_PAWNSa" id="X_358_THE_SIX_PAWNSa"></a><a href="#X_358_THE_SIX_PAWNS"><b>358.—THE SIX PAWNS.—<i>solution</i></b></a></p> + +<p>The general formula for six pawns on all squares greater than 2<sup>2</sup> is +this: Six times the square of the number of combinations of <i>n</i> things +taken three at a time, where <i>n</i> represents the number of squares on +the side of the board. Of course, where <i>n</i> is even the unoccupied +squares in the rows and columns will be even, and where <i>n</i> is odd the +number of squares will be odd. Here <i>n</i> is 8, so the answer is 18,816 +different ways. This is "The Dyer's Puzzle" (<i>Canterbury Puzzles</i>, No. +27) in another form. I repeat it here in order to explain a method of +solving that will be readily grasped by the novice. First of all, it +is evident that if we put a pawn on any line, we must put a second one +in that line in order that the remainder may be even in number. We +cannot put four or six in any row without making it impossible to get +an even number in all the columns interfered with. We have, therefore, +to put two pawns in each of three rows and in each of three columns. +Now, there are just six schemes or arrangements that fulfil these +conditions, and these are shown in Diagrams A to F, inclusive, on next +page.</p> + +<p><span class='pagenum'>Pg 234<a name="Page_234" id="Page_234"></a></span></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a358.png" width="400" height="218" alt="" title="" /> +</div> + +<p>I will just remark in passing that A and B are the only distinctive +arrangements, because, if you give A a quarter-turn, you get F; and if +you give B three quarter-turns in the direction that a clock hand +moves, you will get successively C, D, and E. No matter how you may +place your six pawns, if you have complied with the conditions of the +puzzle they will fall under one of these arrangements. Of course it +will be understood that mere expansions do not destroy the essential +character of the arrangements. Thus G is only an expansion of form A. +The solution therefore consists in finding the number of these +expansions. Supposing we confine our operations to the first three +rows, as in G, then with the pairs <i>a</i> and <i>b</i> placed in the first and +second columns the pair <i>c</i> may be disposed in any one of the +remaining six columns, and so give six solutions. Now slide pair <i>b</i> +into the third column, and there are five possible positions for <i>c</i>. +Slide <i>b</i> into the fourth column, and <i>c</i> may produce four new +solutions. And so on, until (still leaving <i>a</i> in the first column) +you have <i>b</i> in the seventh column, and there is only one place for +<i>c</i>—in the eighth column. Then you may put <i>a</i> in the second column, +<i>b</i> in the third, and <i>c</i> in the fourth, and start sliding <i>c</i> and <i>b</i> +as before for another series of solutions.</p> + +<p>We find thus that, by using form A alone and confining our operations +to the three top rows, we get as many answers as there are +combinations of 8 things taken 3 at a time. This is <sup>(8 × 7 × 6)</sup>/<sub>(1 × +2 × 3)</sub> = 56. And it will at once strike the reader that if there are +56 different ways of electing the columns, there must be for each of +these ways just 56 ways of selecting the rows, for we may +simultaneously work that "sliding" process downwards to the very +bottom in exactly the same way as we have worked from left to right. +Therefore the total number of ways in which form A may be applied is +56 × 6 = 3,136. But there are, as we have seen, six arrangements, and +we have only dealt with one of these, A. We must, therefore, multiply +this result by 6, which gives us 3,136 × 6 = 18,816, which is the +total number of ways, as we have already stated.</p> + +<hr style="width: 30%;" /> +<p><a name="X_359_COUNTER_SOLITAIREa" id="X_359_COUNTER_SOLITAIREa"></a><a href="#X_359_COUNTER_SOLITAIRE"><b>359.—COUNTER SOLITAIRE.—<i>solution</i></b></a></p> + +<p>Play as follows: 3—11, 9—10, 1—2, 7—15, 8—16, 8—7, 5—13, 1—4, +8—5, 6—14, 3—8, 6—3, 6—12, 1—6, 1—9, and all the counters will +have been removed, with the exception of No. 1, as required by the +conditions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_360_CHESSBOARD_SOLITAIREa" id="X_360_CHESSBOARD_SOLITAIREa"></a><a href="#X_360_CHESSBOARD_SOLITAIRE"><b>360.—CHESSBOARD SOLITAIRE.—<i>solution</i></b></a></p> + +<p>Play as follows: 7—15, 8—16, 8—7, 2—10, 1—9, 1—2, 5—13, 3—4, +6—3, 11—1, 14—8, 6—12, 5—6, 5—11, 31—23, 32—24, 32—31, +26—18, 25—17, 25—26, 22—32, 14—22, 29—21, 14—29, 27—28, +30—27, 25—14, 30—20, 25—30, 25—5. The two counters left on the +board are 25 and 19—both belonging to the same group, as +stipulated—and 19 has never been moved from its original place.</p> + +<p>I do not think any solution is possible in which only one counter is +left on the board.</p> + +<hr style="width: 30%;" /> +<p><a name="X_361_THE_MONSTROSITYa" id="X_361_THE_MONSTROSITYa"></a><a href="#X_361_THE_MONSTROSITY"><b>361.—THE MONSTROSITY.—<i>solution</i></b></a></p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'></td><td align='center'>White</td><td align='center'>Black,</td></tr> +<tr><td align='right'>1.</td><td align='left'>P to KB 4</td><td align='left'>P to QB 3</td></tr> +<tr><td align='right'>2.</td><td align='left'>K to B 2</td><td align='left'>Q to R 4</td></tr> +<tr><td align='right'>3.</td><td align='left'>K to K 3</td><td align='left'>K to Q sq</td></tr> +<tr><td align='right'>4.</td><td align='left'>P to B 5</td><td align='left'>K to B 2</td></tr> +<tr><td align='right'>5.</td><td align='left'>Q to K sq</td><td align='left'>K to Kt 3</td></tr> +<tr><td align='right'>6.</td><td align='left'>Q to Kt 3</td><td align='left'>Kt to QR 3</td></tr> +<tr><td align='right'>7.</td><td align='left'>Q to Kt 8</td><td align='left'>P to KR 4</td></tr> +<tr><td align='right'>8.</td><td align='left'>Kt to KB 3</td><td align='left'>R to R 3</td></tr> +<tr><td align='right'>9.</td><td align='left'>Kt to K 5</td><td align='left'>R to Kt 3</td></tr> +<tr><td align='right'>10.</td><td align='left'>Q takes B</td><td align='left'>R to Kt 6, ch</td></tr> +<tr><td align='right'>11.</td><td align='left'>P takes R</td><td align='left'>K to Kt 4</td></tr> +<tr><td align='right'>12.</td><td align='left'>R to R 4</td><td align='left'>P to B 3</td></tr> +<tr><td align='right'>13.</td><td align='left'>R to Q 4</td><td align='left'>P takes Kt</td></tr> +<tr><td align='right'>14.</td><td align='left'>P to QKt 4</td><td align='left'>P takes R, ch</td></tr> +<tr><td align='right'>15.</td><td align='left'>K to B 4</td><td align='left'>P to R 5</td></tr> +<tr><td align='right'>16.</td><td align='left'>Q to K 8</td><td align='left'>P to R 6</td></tr> +<tr><td align='right'>17.</td><td align='left'>Kt to B 3, ch</td><td align='left'>P takes Kt</td></tr> +<tr><td align='right'>18.</td><td align='left'>B to R 3</td><td align='left'>P to R 7</td></tr> +<tr><td align='right'>19.</td><td align='left'>R to Kt sq</td><td align='left'>P to R 8 (Q)</td></tr> +<tr><td align='right'>20.</td><td align='left'>R to Kt 2</td><td align='left'>P takes R</td></tr> +<tr><td align='right'>21.</td><td align='left'>K to Kt 5</td><td align='left'>Q to KKt 8</td></tr> +<tr><td align='right'>22.</td><td align='left'>Q to R 5</td><td align='left'>K to R 5</td></tr> +<tr><td align='right'>23.</td><td align='left'>P to Kt 5</td><td align='left'>R to B sq</td></tr> +<tr><td align='right'>24.</td><td align='left'>P to Kt 6</td><td align='left'>R to B 2</td></tr> +<tr><td align='right'>25.</td><td align='left'>P takes R</td><td align='left'>P to Kt 8 (B)</td></tr> +<tr><td align='right'>26.</td><td align='left'>P to B 8 (R)</td><td align='left'>Q to B 2</td></tr> +<tr><td align='right'>27.</td><td align='left'>B to Q 6</td><td align='left'>Kt to Kt 5</td></tr> +<tr><td align='right'>28.</td><td align='left'>K to Kt 6</td><td align='left'>K to R 6</td></tr> +<tr><td align='right'>29.</td><td align='left'>R to R 8</td><td align='left'>K to Kt 7</td></tr> +<tr><td align='right'>30.</td><td align='left'>P to R 4</td><td align='left'>Q (Kt 8) to Kt 3</td></tr> +<tr><td align='right'>31.</td><td align='left'>P to R 5</td><td align='left'>K to B 8</td></tr> +<tr><td align='right'>32.</td><td align='left'>P takes Q</td><td align='left'>K to Q 8</td></tr> +<tr><td align='right'>33.</td><td align='left'>P takes Q</td><td align='left'>K to K 8</td></tr> +<tr><td align='right'>34.</td><td align='left'>K to B 7</td><td align='left'>Kt to KR 3, ch</td></tr> +<tr><td align='right'>35.</td><td align='left'>K to K 8</td><td align='left'>B to R 7</td></tr> +<tr><td align='right'>36.</td><td align='left'>P to B 6</td><td align='left'>B to Kt sq</td></tr> +<tr><td align='right'>37.</td><td align='left'>P to B 7</td><td align='left'>K takes B</td></tr> +<tr><td align='right'>38.</td><td align='left'>P to B 8 (B)</td><td align='left'>Kt to Q 4</td></tr> +<tr><td align='right'>39.</td><td align='left'>B to Kt 8</td><td align='left'>Kt to B 3, ch</td></tr> +<tr><td align='right'>40.</td><td align='left'>K to Q 8</td><td align='left'>Kt to K sq</td></tr> +<tr><td align='right'>41.</td><td align='left'>P takes Kt (R)</td><td align='left'>Kt to B 2, ch</td></tr> +<tr><td align='right'>42.</td><td align='left'>K to B 7</td><td align='left'>Kt to Q sq</td></tr> +<tr><td align='right'>43.</td><td align='left'>Q to B 7, ch</td><td align='left'>K to Kt 8</td></tr> +</table></div> + +<p>And the position is reached.</p> + +<p>The order of the moves is immaterial, and this order may be greatly +varied. But, al<span class='pagenum'>Pg 235<a name="Page_235" id="Page_235"></a></span>though many attempts have been made, nobody has +succeeded in reducing the number of my moves.</p> + + +<hr style="width: 30%;" /> +<p><a name="X_362_THE_WASSAIL_BOWLa" id="X_362_THE_WASSAIL_BOWLa"></a><a href="#X_362_THE_WASSAIL_BOWL"><b>362.—THE WASSAIL BOWL.—<i>solution</i></b></a></p> + + +<p>The division of the twelve pints of ale can be made in eleven +manipulations, as below. The six columns show at a glance the quantity +of ale in the barrel, the five-pint jug, the three-pint jug, and the +tramps X, Y, and Z respectively after each manipulation.</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>Barrel.</td><td></td><td align='center'>5-pint.</td><td></td><td align='center'>3-pint.</td><td></td><td align='center'>X.</td><td></td><td align='center'>Y.</td><td></td><td align='center'>Z.</td></tr> +<tr><td align='center'>7</td><td align='center'>..</td><td align='center'>5</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>7</td><td align='center'>..</td><td align='center'>2</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>7</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>2</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>7</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>2</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>4</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>2</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>0</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>2</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>0</td><td align='center'>..</td><td align='center'>5</td><td align='center'>..</td><td align='center'>1</td><td align='center'>..</td><td align='center'>2</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>0</td><td align='center'>..</td><td align='center'>5</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>2</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>1</td></tr> +<tr><td align='center'>0</td><td align='center'>..</td><td align='center'>2</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>2</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>1</td></tr> +<tr><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>1</td></tr> +<tr><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>4</td></tr> +</table></div> + + +<p>And each man has received his four pints of ale.</p> + + +<hr style="width: 30%;" /> +<p><a name="X_363_THE_DOCTORS_QUERYa" id="X_363_THE_DOCTORS_QUERYa"></a><a href="#X_363_THE_DOCTORS_QUERY"><b>363.—THE DOCTOR'S QUERY.—<i>solution</i></b></a></p> + + +<p>The mixture of spirits of wine and water is in the proportion of 40 to +1, just as in the other bottle it was in the proportion of 1 to 40.</p> + + +<hr style="width: 30%;" /> +<p><a name="X_364_THE_BARREL_PUZZLEa" id="X_364_THE_BARREL_PUZZLEa"></a><a href="#X_364_THE_BARREL_PUZZLE"><b>364.—THE BARREL PUZZLE.—<i>solution</i></b></a></p> + + +<div class="figcenter" style="width: 400px;"> +<img src="images/a364.png" width="400" height="296" alt="" title="" /> +</div> + +<p>All that is necessary is to tilt the barrel as in Fig. 1, and if the +edge of the surface of the water exactly touches the lip <i>a</i> at the +same time that it touches the edge of the bottom <i>b</i>, it will be just +half full. To be more exact, if the bottom is an inch or so from the +ground, then we can allow for that, and the thickness of the bottom, +at the top. If when the surface of the water reached the lip <i>a</i> it +had risen to the point <i>c</i> in Fig. 2, then it would be more than half +full. If, as in Fig. 3, some portion of the bottom were visible and +the level of the water fell to the point <i>d</i>, then it would be less +than half full.</p> + +<p>This method applies to all symmetrically constructed vessels.</p> + + +<hr style="width: 30%;" /> +<p><a name="X_365_NEW_MEASURING_PUZZLEa" id="X_365_NEW_MEASURING_PUZZLEa"></a><a href="#X_365_NEW_MEASURING_PUZZLE"><b>365.—NEW MEASURING PUZZLE.—<i>solution</i></b></a></p> + + +<p>The following solution in eleven manipulations shows the contents of +every vessel at the start and after every manipulation:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>10-quart.</td><td></td><td align='center'>10-quart.</td><td></td><td align='center'>5-quart.</td><td></td><td align='center'>4-quart.</td></tr> +<tr><td align='center'>10</td><td align='center'>..</td><td align='center'>10</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>5</td><td align='center'>..</td><td align='center'>10</td><td align='center'>..</td><td align='center'>5</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>5</td><td align='center'>..</td><td align='center'>10</td><td align='center'>..</td><td align='center'>1</td><td align='center'>..</td><td align='center'>4</td></tr> +<tr><td align='center'>9</td><td align='center'>..</td><td align='center'>10</td><td align='center'>..</td><td align='center'>1</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>9</td><td align='center'>..</td><td align='center'>6</td><td align='center'>..</td><td align='center'>1</td><td align='center'>..</td><td align='center'>4</td></tr> +<tr><td align='center'>9</td><td align='center'>..</td><td align='center'>7</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>4</td></tr> +<tr><td align='center'>9</td><td align='center'>..</td><td align='center'>7</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>0</td></tr> +<tr><td align='center'>9</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>4</td><td align='center'>..</td><td align='center'>4</td></tr> +<tr><td align='center'>9</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>5</td><td align='center'>..</td><td align='center'>3</td></tr> +<tr><td align='center'>9</td><td align='center'>..</td><td align='center'>8</td><td align='center'>..</td><td align='center'>0</td><td align='center'>..</td><td align='center'>3</td></tr> +<tr><td align='center'>4</td><td align='center'>..</td><td align='center'>8</td><td align='center'>..</td><td align='center'>5</td><td align='center'>..</td><td align='center'>3</td></tr> +<tr><td align='center'>4</td><td align='center'>..</td><td align='center'>10</td><td align='center'>..</td><td align='center'>3</td><td align='center'>..</td><td align='center'>3</td></tr> +</table></div> + + + +<hr style="width: 30%;" /> +<p><a name="X_366_THE_HONEST_DAIRYMANa" id="X_366_THE_HONEST_DAIRYMANa"></a><a href="#X_366_THE_HONEST_DAIRYMAN"><b>366.—THE HONEST DAIRYMAN.—<i>solution</i></b></a></p> + + +<p>Whatever the respective quantities of milk and water, the relative +proportion sent to London would always be three parts of water to one +of milk. But there are one or two points to be observed. There must +originally be more water than milk, or there will be no water in A to +double in the second transaction. And the water must not be more than +three times the quantity of milk, or there will not be enough liquid +in B to effect the second transaction. The third transaction has no +effect on A, as the relative proportions in it must be the same as +after the second transaction. It was introduced to prevent a quibble +if the quantity of milk and water were originally the same; for though +double "nothing" would be "nothing," yet the third transaction in such +a case could not take place.</p> + + +<hr style="width: 30%;" /> +<p><a name="X_367_WINE_AND_WATERa" id="X_367_WINE_AND_WATERa"></a><a href="#X_367_WINE_AND_WATER"><b>367.—WINE AND WATER.—<i>solution</i></b></a></p> + + +<p>The wine in small glass was one-sixth of the total liquid, and the +wine in large glass two-ninths of total. Add these together, and we +find that the wine was seven-eighteenths of total fluid, and therefore +the water eleven-eighteenths.</p> + + +<hr style="width: 30%;" /> +<p><a name="X_368_THE_KEG_OF_WINEa" id="X_368_THE_KEG_OF_WINEa"></a><a href="#X_368_THE_KEG_OF_WINE"><b>368.—THE KEG OF WINE.—<i>solution</i></b></a></p> + + +<p>The capacity of the jug must have been a little less than three +gallons. To be more exact, it was 2.93 gallons.</p> + + +<hr style="width: 30%;" /> +<p><a name="X_369_MIXING_THE_TEAa" id="X_369_MIXING_THE_TEAa"></a><a href="#X_369_MIXING_THE_TEA"><b>369.—MIXING THE TEA.—<i>solution</i></b></a></p> + + +<p>There are three ways of mixing the teas. Taking them in the order of +quality, 2<i>s</i>. 6<i>d</i>., 2<i>s</i>. 3<i>d</i>., 1<i>s</i>. 9p., mix 16 lbs., 1 lb., 3 lbs.; or 14 +lbs., 4 lbs., 2 lbs.; or 12 lbs., 7 lbs., 1 lb. In every case the +twenty pounds mixture should be worth 2<i>s</i>. 4½<i>d</i>. per pound; but the +last case requires the smallest quantity of the best tea, therefore it +is the correct answer.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 236<a name="Page_236" id="Page_236"></a></span><a name="X_370_A_PACKING_PUZZLEa" id="X_370_A_PACKING_PUZZLEa"></a><a href="#X_370_A_PACKING_PUZZLE"><b>370.—A PACKING PUZZLE.—<i>solution</i></b></a></p> + +<p>On the side of the box, 14 by 22<sup>4</sup>/<sub>5</sub>, we can arrange 13 rows +containing alternately 7 and 6 balls, or 85 in all. Above this we can +place another layer consisting of 12 rows of 7 and 6 alternately, or a +total of 78. In the length of 24<sup>9</sup>/<sub>10</sub> inches 15 such layers may be +packed, the alternate layers containing 85 and 78 balls. Thus 8 times +85 added to 7 times 78 gives us 1,226 for the full contents of the +box.</p> + +<hr style="width: 30%;" /> +<p><a name="X_371_GOLD_PACKING_IN_RUSSIAa" id="X_371_GOLD_PACKING_IN_RUSSIAa"></a><a href="#X_371_GOLD_PACKING_IN_RUSSIA"><b>371.—GOLD PACKING IN RUSSIA.—<i>solution</i></b></a></p> + +<p>The box should be 100 inches by 100 inches by 11 inches deep, internal +dimensions. We can lay flat at the bottom a row of eight slabs, +lengthways, end to end, which will just fill one side, and nine of +these rows will dispose of seventy-two slabs (all on the bottom), with +a space left over on the bottom measuring 100 inches by 1 inch by 1 +inch. Now make eleven depths of such seventy-two slabs, and we have +packed 792, and have a space 100 inches by 1 inch by 11 inches deep. +In this we may exactly pack the remaining eight slabs on edge, end to +end.</p> + +<hr style="width: 30%;" /> +<p><a name="X_372_THE_BARRELS_OF_HONEYa" id="X_372_THE_BARRELS_OF_HONEYa"></a><a href="#X_372_THE_BARRELS_OF_HONEY"><b>372.—THE BARRELS OF HONEY.—<i>solution</i></b></a></p> + +<p>The only way in which the barrels could be equally divided among the +three brothers, so that each should receive his 3½ barrels of honey +and his 7 barrels, is as follows:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'></td><td align='center'>Full.</td><td align='center'>Half-full.</td><td align='center'>Empty.</td></tr> +<tr><td align='center'>A</td><td align='center'>3</td><td align='center'>1</td><td align='center'>3</td></tr> +<tr><td align='center'>B</td><td align='center'>2</td><td align='center'>3</td><td align='center'>2</td></tr> +<tr><td align='center'>C</td><td align='center'>2</td><td align='center'>3</td><td align='center'>2</td></tr> +</table></div> + +<p>There is one other way in which the division could be made, were it +not for the objection that all the brothers made to taking more than +four barrels of the same description. Except for this difficulty, they +might have given B his quantity in exactly the same way as A above, +and then have left C one full barrel, five half-full barrels, and one +empty barrel. It will thus be seen that in any case two brothers would +have to receive their allowance in the same way.</p> + +<hr style="width: 30%;" /> +<p><a name="X_373_CROSSING_THE_STREAMa" id="X_373_CROSSING_THE_STREAMa"></a><a href="#X_373_CROSSING_THE_STREAM"><b>373.—CROSSING THE STREAM.—<i>solution</i></b></a></p> + +<p>First, the two sons cross, and one returns Then the man crosses and +the other son returns. Then both sons cross and one returns. Then the +lady crosses and the other son returns Then the two sons cross and one +of them returns for the dog. Eleven crossings in all.</p> + +<p>It would appear that no general rule can be given for solving these +river-crossing puzzles. A formula can be found for a particular case +(say on No. <a href="#X_375_FIVE_JEALOUS_HUSBANDSa">375</a> or <a href="#X_376_THE_FOUR_ELOPEMENTSa">376</a>) that would apply to any number of individuals +under the restricted conditions; but it is not of much use, for some +little added stipulation will entirely upset it. As in the case of the +measuring puzzles, we generally have to rely on individual ingenuity.</p> + +<hr style="width: 30%;" /> +<p><a name="X_374_CROSSING_THE_RIVER_AXEa" id="X_374_CROSSING_THE_RIVER_AXEa"></a><a href="#X_374_CROSSING_THE_RIVER_AXE"><b>374.—CROSSING THE RIVER AXE.—<i>solution</i></b></a></p> + +<p>Here is the solution:—</p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'></td><td align='center'>{J 5)</td><td align='center'>G T8 3</td></tr> +<tr><td align='center'>5</td><td align='center'>( J }</td><td align='center'>G T8 3</td></tr> +<tr><td align='center'>5</td><td align='center'>{G 3)</td><td align='center'>JT8</td></tr> +<tr><td align='center'>53</td><td align='center'>( G }</td><td align='center'>JT8</td></tr> +<tr><td align='center'>53</td><td align='center'>{J T)</td><td align='center'>G 8</td></tr> +<tr><td align='center'>J 5</td><td align='center'>(T 3}</td><td align='center'>G 8</td></tr> +<tr><td align='center'>J 5</td><td align='center'>{G 8)</td><td align='center'>T 3</td></tr> +<tr><td align='center'>G 8</td><td align='center'>(J 5}</td><td align='center'>T</td></tr> +<tr><td align='center'>G 8</td><td align='center'>{J T)</td><td align='center'>53</td></tr> +<tr><td align='center'>JT8</td><td align='center'>( G }</td><td align='center'>53</td></tr> +<tr><td align='center'>JT8</td><td align='center'>{G 3)</td><td align='center'>5</td></tr> +<tr><td align='center'>G T8 3</td><td align='center'>( J }</td><td align='center'>5</td></tr> +<tr><td align='center'>G T8 3</td><td align='center'>{J 5)</td><td></td></tr> +</table></div> + +<p>G, J, and T stand for Giles, Jasper, and Timothy; and 8, 5, 3, for +£800, £500, and £300 respectively. The two side columns represent the +left bank and the right bank, and the middle column the river. +Thirteen crossings are necessary, and each line shows the position +when the boat is in mid-stream during a crossing, the point of the +bracket indicating the direction.</p> + +<p>It will be found that not only is no person left alone on the land or +in the boat with more than his share of the spoil, but that also no +two persons are left with more than their joint shares, though this +last point was not insisted upon in the conditions.</p> + +<hr style="width: 30%;" /> +<p><a name="X_375_FIVE_JEALOUS_HUSBANDSa" id="X_375_FIVE_JEALOUS_HUSBANDSa"></a><a href="#X_375_FIVE_JEALOUS_HUSBANDS"><b>375.—FIVE JEALOUS HUSBANDS.—<i>solution</i></b></a></p> + +<p>It is obvious that there must be an odd number of crossings, and that +if the five husbands had not been jealous of one another the party +might have all got over in nine crossings. But no wife was to be in +the company of a man or men unless her husband was present. This +entails two more crossings, eleven in all.</p> + +<p>The following shows how it might have been done. The capital letters +stand for the husbands, and the small letters for their respective +wives. The position of affairs is shown at the start, and after each +crossing between the left bank and the right, and the boat is +represented by the asterisk. So you can see at a glance that a, b, and +c went over at the first crossing, that b and c returned at the second +crossing, and so on.<span class='pagenum'>Pg 237<a name="Page_237" id="Page_237"></a></span></p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td></td><td align='center'> ABCDE abcde *</td><td align='center'>..</td><td></td></tr> +<tr><td align='right'>1.</td><td align='center'> ABCDE de </td><td align='center'>..</td><td align='center'>* abc</td></tr> +<tr><td align='right'>2.</td><td align='center'> ABCDE bcde *</td><td align='center'>..</td><td align='center'> a</td></tr> +<tr><td align='right'>3.</td><td align='center'> ABCDE e </td><td align='center'>..</td><td align='center'>* abcd</td></tr> +<tr><td align='right'>4.</td><td align='center'> ABCDE de *</td><td align='center'>..</td><td align='center'> abc</td></tr> +<tr><td align='right'>5.</td><td align='center'> DE de </td><td align='center'>..</td><td align='center'>* ABC abc</td></tr> +<tr><td align='right'>6.</td><td align='center'> CDE cde *</td><td align='center'>..</td><td align='center'> AB ab</td></tr> +<tr><td align='right'>7.</td><td align='center'> cde </td><td align='center'>..</td><td align='center'>* ABCDE ab</td></tr> +<tr><td align='right'>8.</td><td align='center'> bcde *</td><td align='center'>..</td><td align='center'> ABCDE a</td></tr> +<tr><td align='right'>9.</td><td align='center'> e </td><td align='center'>..</td><td align='center'>* ABCDE abcd</td></tr> +<tr><td align='right'>10.</td><td align='center'> bc e *</td><td align='center'>..</td><td align='center'> ABCDE a d</td></tr> +<tr><td align='right'>11.</td><td align='center'> </td><td align='center'>..</td><td align='center'>* ABCDE abcde</td></tr> +</table></div> + +<p>There is a little subtlety concealed in the words "show the <i>quickest</i> +way."</p> + +<p>Everybody correctly assumes that, as we are told nothing of the rowing +capabilities of the party, we must take it that they all row equally +well. But it is obvious that two such persons should row more quickly +than one.</p> + +<p>Therefore in the second and third crossings two of the ladies should +take back the boat to fetch d, not one of them only. This does not +affect the number of landings, so no time is lost on that account. A +similar opportunity occurs in crossings 10 and 11, where the party +again had the option of sending over two ladies or one only.</p> + +<p>To those who think they have solved the puzzle in nine crossings I +would say that in every case they will find that they are wrong. No +such jealous husband would, in the circumstances, send his wife over +to the other bank to a man or men, even if she assured him that she +was coming back next time in the boat. If readers will have this fact +in mind, they will at once discover their errors.</p> + +<hr style="width: 30%;" /> +<p><a name="X_376_THE_FOUR_ELOPEMENTSa" id="X_376_THE_FOUR_ELOPEMENTSa"></a><a href="#X_376_THE_FOUR_ELOPEMENTS"><b>376.—THE FOUR ELOPEMENTS.—<i>solution</i></b></a></p> + +<p>If there had been only three couples, the island might have been +dispensed with, but with four or more couples it is absolutely +necessary in order to cross under the conditions laid down. It can be +done in seventeen passages from land to land (though French +mathematicians have declared in their books that in such circumstances +twenty-four are needed), and it cannot be done in fewer. I will give +one way. A, B, C, and D are the young men, and a, b, c, and d are the +girls to whom they are respectively engaged. The three columns show +the positions of the different individuals on the lawn, the island, +and the opposite shore before starting and after each passage, while +the asterisk indicates the position of the boat on every occasion.</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'>Lawn.</td><td align='center'>Island.</td><td align='center'>Shore.</td></tr> +<tr><td align='center'>ABCDabcd *</td><td align='center'></td><td></td></tr> +<tr><td align='center'>ABCD cd</td><td align='center'></td><td align='center'>ab *</td></tr> +<tr><td align='center'>ABCD bcd *</td><td align='center'></td><td align='center'>a</td></tr> +<tr><td align='center'>ABCD d</td><td align='center'>bc *</td><td align='center'>a</td></tr> +<tr><td align='center'>ABCD cd *</td><td align='center'>b</td><td align='center'>a</td></tr> +<tr><td align='center'>CD cd</td><td align='center'>b</td><td align='center'>AB a *</td></tr> +<tr><td align='center'>BCD cd *</td><td align='center'>b</td><td align='center'>A a</td></tr> +<tr><td align='center'>BCD</td><td align='center'>bcd *</td><td align='center'>A a</td></tr> +<tr><td align='center'>BCD d *</td><td align='center'>bc</td><td align='center'>A a</td></tr> +<tr><td align='center'>D d</td><td align='center'>bc</td><td align='center'>ABC a *</td></tr> +<tr><td align='center'>D d</td><td align='center'>abc *</td><td align='center'>ABC</td></tr> +<tr><td align='center'>D d</td><td align='center'>b</td><td align='center'>ABC a c *</td></tr> +<tr><td align='center'>B D d *</td><td align='center'>b</td><td align='center'>A C a c</td></tr> +<tr><td align='center'>d</td><td align='center'>b</td><td align='center'>ABCD a c *</td></tr> +<tr><td align='center'>d</td><td align='center'>bc *</td><td align='center'>ABCD a</td></tr> +<tr><td align='center'>d</td><td align='center'></td><td align='center'>ABCD abc *</td></tr> +<tr><td align='center'>cd *</td><td align='center'></td><td align='center'>ABCD ab</td></tr> +<tr><td align='center'></td><td align='center'></td><td align='center'>ABCD abcd *</td></tr> +</table></div> + + +<p>Having found the fewest possible passages, we should consider two +other points in deciding on the "quickest method": Which persons were +the most expert in handling the oars, and which method entails the +fewest possible delays in getting in and out of the boat? We have no +data upon which to decide the first point, though it is probable that, +as the boat belonged to the girls' household, they would be capable +oarswomen. The other point, however, is important, and in the solution +I have given (where the girls do 8-13ths of the rowing and A and D +need not row at all) there are only sixteen gettings-in and sixteen +gettings-out. A man and a girl are never in the boat together, and no +man ever lands on the island. There are other methods that require +several more exchanges of places.</p> + +<hr style="width: 30%;" /> +<p><a name="X_377_STEALING_THE_CASTLE_TREASUREa" id="X_377_STEALING_THE_CASTLE_TREASUREa"></a><a href="#X_377_STEALING_THE_CASTLE_TREASURE"><b>377.—STEALING THE CASTLE TREASURE.—<i>solution</i></b></a></p> + +<p>Here is the best answer, in eleven manipulations:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Treasure down.</td></tr> +<tr><td align='left'>Boy down—treasure up.</td></tr> +<tr><td align='left'>Youth down—boy up.</td></tr> +<tr><td align='left'>Treasure down.</td></tr> +<tr><td align='left'>Man down—youth and treasure up.</td></tr> +<tr><td align='left'>Treasure down.</td></tr> +<tr><td align='left'>Boy down—treasure up.</td></tr> +<tr><td align='left'>Treasure down.</td></tr> +<tr><td align='left'>Youth down—boy up.</td></tr> +<tr><td align='left'>Boy down—treasure up.</td></tr> +<tr><td align='left'>Treasure down.</td></tr> +</table></div> + +<hr style="width: 30%;" /> +<p><a name="X_378_DOMINOES_IN_PROGRESSIONa" id="X_378_DOMINOES_IN_PROGRESSIONa"></a><a href="#X_378_DOMINOES_IN_PROGRESSION"><b>378.—DOMINOES IN PROGRESSION.—<i>solution</i></b></a></p> + +<p>There are twenty-three different ways. You may start with any domino, +except the 4—4 and those that bear a 5 or 6, though only certain +initial dominoes may be played either way round. If you are given the +common difference and the first domino is played, you have no option +as to the other dominoes. Therefore all I need do is to give the +initial domino for all the twenty-three ways, and state the common +difference. This I will do as follows:—</p> + +<p>With a common difference of 1, the first domino may be either of +these: 0—0, 0—1, 1—0, 0—2, 1—1, 2—0, 0—3, 1—2, 2—1, 3—0, +0—4, 1—3, 2—2, 3—1, 1—4, 2—3, 3—2, 2—4, 3—3, 3—4. With a +difference of 2, the first domino may be 0—0, 0—2, or 0—1. Take the +last case of all as an example. Having played the 0—1, and the +difference being 2, we are <span class='pagenum'>Pg 238<a name="Page_238" id="Page_238"></a></span>compelled to continue with 1—2, 2—3, +3—4. 4—5, 5—6. There are three dominoes that can never be used at +all. These are 0—5, 0—6, and 1—6. If we used a box of dominoes +extending to 9—9, there would be forty different ways.</p> + +<hr style="width: 30%;" /> +<p><a name="X_379_THE_FIVE_DOMINOESa" id="X_379_THE_FIVE_DOMINOESa"></a><a href="#X_379_THE_FIVE_DOMINOES"><b>379.—THE FIVE DOMINOES.—<i>solution</i></b></a></p> + +<p>There are just ten different ways of arranging the dominoes. Here is +one of them:—</p> + +<p>(2—0) (0—0) (0—1) (1—4) (4—0).</p> + +<p>I will leave my readers to find the remaining nine for themselves.</p> + +<hr style="width: 30%;" /> +<p><a name="X_380_THE_DOMINO_FRAME_PUZZLEa" id="X_380_THE_DOMINO_FRAME_PUZZLEa"></a><a href="#X_380_THE_DOMINO_FRAME_PUZZLE"><b>380.—THE DOMINO FRAME PUZZLE.—<i>solution</i></b></a></p> + + +<div class="figcenter" style="width: 400px;"> +<img src="images/a380.png" width="400" height="400" alt="" title="" /> +</div> + +<p>The illustration is a solution. It will be found that all four sides +of the frame add up 44. The sum of the pips on all the dominoes is +168, and if we wish to make the sides sum to 44, we must take care +that the four corners sum to 8, because these corners are counted +twice, and 168 added to 8 will equal 4 times 44, which is necessary. +There are many different solutions. Even in the example given certain +interchanges are possible to produce different arrangements. For +example, on the left-hand side the string of dominoes from 2—2 down +to 3—2 may be reversed, or from 2—6 to 3—2, or from 3—0 to 5—3. +Also, on the right-hand side we may reverse from 4—3 to 1—4. These +changes will not affect the correctness of the solution.</p> + +<hr style="width: 30%;" /> +<p><a name="X_381_THE_CARD_FRAME_PUZZLEa" id="X_381_THE_CARD_FRAME_PUZZLEa"></a><a href="#X_381_THE_CARD_FRAME_PUZZLE"><b>381.—THE CARD FRAME PUZZLE.—<i>solution</i></b></a></p> + +<p>The sum of all the pips on the ten cards is 55. Suppose we are trying +to get 14 pips on every side. Then 4 times 14 is 56. But each of the +four corner cards is added in twice, so that 55 deducted from 56, or +1, must represent the sum of the four corner cards. This is clearly +impossible; therefore 14 is also impossible. But suppose we came to +trying 18. Then 4 times 18 is 72, and if we deduct 55 we get 17 as the +sum of the corners. We need then only try different arrangements with +the four corners always summing to 17, and we soon discover the +following solution:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a381.png" width="400" height="401" alt="" title="" /> +</div> + +<p>The final trials are very limited in number, and must with a little +judgment either bring us to a correct solution or satisfy us that a +solution is impossible under the conditions we are attempting. The two +centre cards on the upright sides can, of course, always be +interchanged, but I do not call these different solutions. If you +reflect in a mirror you get another arrangement, which also is not +considered different. In the answer given, however, we may exchange +the 5 with the 8 and the 4 with the 1. This is a different solution. +There are two solutions with 18, four with 19, two with 20, and two +with 22—ten arrangements in all. Readers may like to find all these +for themselves.</p> + +<hr style="width: 30%;" /> +<p><a name="X_382_THE_CROSS_OF_CARDSa" id="X_382_THE_CROSS_OF_CARDSa"></a><a href="#X_382_THE_CROSS_OF_CARDS"><b>382.—THE CROSS OF CARDS.—<i>solution</i></b></a></p> + +<p>There are eighteen fundamental arrangements, as follows, where I only +give the numbers in the horizontal bar, since the remainder must +naturally fall into their places.</p> + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="0" summary=""> +<tr><td align='center'>5 6 1 7 4</td></tr> +<tr><td align='center'>3 5 1 6 8</td></tr> +<tr><td align='center'>3 4 1 7 8</td></tr> +<tr><td align='center'>2 5 1 7 8</td></tr> +<tr><td align='center'>2 5 3 6 8</td></tr> +<tr><td align='center'>1 5 3 7 8</td></tr> +<tr><td align='center'>2 4 3 7 8</td></tr> +<tr><td align='center'>1 4 5 7 8</td></tr> +<tr><td align='center'>2 3 5 7 8</td></tr> +<tr><td align='center'>2 4 5 6 8</td></tr> +<tr><td align='center'>3 4 5 6 7</td></tr> +<tr><td align='center'>1 4 7 6 8</td></tr> +<tr><td align='center'>2 3 7 6 8</td></tr> +<tr><td align='center'>2 4 7 5 8</td></tr> +<tr><td align='center'>3 4 9 5 6</td></tr> +<tr><td align='center'>2 4 9 5 7</td></tr> +<tr><td align='center'>1 4 9 6 7</td></tr> +<tr><td align='center'>2 3 9 6 7</td></tr> +</table></div> + +<p>It will be noticed that there must always be an odd number in the +centre, that there are four ways each of adding up 23, 25, and 27, but +only three ways each of summing to 24 and 26.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 239<a name="Page_239" id="Page_239"></a></span><a name="X_383_THE_T_CARD_PUZZLEa" id="X_383_THE_T_CARD_PUZZLEa"></a><a href="#X_383_THE_T_CARD_PUZZLE"><b>383.—THE "T" CARD PUZZLE.—<i>solution</i></b></a></p> + +<p>If we remove the ace, the remaining cards may he divided into two +groups (each adding up alike) in four ways; if we remove 3, there are +three ways; if 5, there are four ways; if 7, there are three ways; and +if we remove 9, there are four ways of making two equal groups. There +are thus eighteen different ways of grouping, and if we take any one +of these and keep the odd card (that I have called "removed") at the +head of the column, then one set of numbers can be varied in order in +twenty-four ways in the column and the other four twenty-four ways in +the horizontal, or together they may be varied in 24 × 24 = 576 ways. +And as there are eighteen such cases, we multiply this number by 18 +and get 10,368, the correct number of ways of placing the cards. As +this number includes the reflections, we must divide by 2, but we have +also to remember that every horizontal row can change places with a +vertical row, necessitating our multiplying by 2; so one operation +cancels the other.</p> + +<hr style="width: 30%;" /> +<p><a name="X_384_CARD_TRIANGLESa" id="X_384_CARD_TRIANGLESa"></a><a href="#X_384_CARD_TRIANGLES"><b>384.—CARD TRIANGLES.—<i>solution</i></b></a></p> + +<p>The following arrangements of the cards show (1) the smallest possible +sum, 17; and (2) the largest possible, 23.</p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/a384.png" width="300" height="100" alt="" title="" /> +</div> + +<p>It will be seen that the two cards in the middle of any side may +always be interchanged without affecting the conditions. Thus there +are eight ways of presenting every fundamental arrangement. The number +of fundamentals is eighteen, as follows: two summing to 17, four +summing to 19, six summing to 20, four summing to 21, and two summing +to 23. These eighteen fundamentals, multiplied by eight (for the +reason stated above), give 144 as the total number of different ways +of placing the cards.</p> + +<hr style="width: 30%;" /> +<p><a name="X_385_STRAND_PATIENCEa" id="X_385_STRAND_PATIENCEa"></a><a href="#X_385_STRAND_PATIENCE"><b>385.—"STRAND" PATIENCE.—<i>solution</i></b></a></p> + +<p>The reader may find a solution quite easy in a little over 200 moves, +but, surprising as it may at first appear, not more than 62 moves are +required. Here is the play: By "4 C up" I mean a transfer of the 4 of +clubs with all the cards that rest on it. 1 D on space, 2 S on space, +3 D on space, 2 S on 3 D, 1 H on 2 S, 2 C on space, 1 D on 2 C, 4 S on +space, 3 H on 4 S (9 moves so far), 2 S up on 3 H (3 moves), 5 H and 5 +D exchanged, and 4 C on 5 D (6 moves), 3 D on 4 C (1), 6 S (with 5 H) +on space (3), 4 C up on 5 H (3), 2 C up on 3 D (3), 7 D on space (1), +6 C up on 7 D (3), 8 S on space (1), 7 H on 8 S (1), 8 C on 9 D (1), 7 +H on 8 C (1), 8 S on 9 H (1), 7 H on 8 S (1), 7 D up on 8 C (5), 4 C +up on 5 D (9), 6 S up on 7 H (3), 4 S up on 5 H (7) = 62 moves in all. +This is my record; perhaps the reader can beat it.</p> + +<hr style="width: 30%;" /> +<p><a name="X_386_A_TRICK_WITH_DICEa" id="X_386_A_TRICK_WITH_DICEa"></a><a href="#X_386_A_TRICK_WITH_DICE"><b>386.—A TRICK WITH DICE.—<i>solution</i></b></a></p> + +<p>All you have to do is to deduct 250 from the result given, and the +three figures in the answer will be the three points thrown with the +dice. Thus, in the throw we gave, the number given would be 386; and +when we deduct 250 we get 136, from which we know that the throws were +1, 3, and 6.</p> + +<p>The process merely consists in giving 100<i>a</i> + 10<i>b</i> + <i>c</i> + 250, where <i>a</i>, +<i>b</i>, and <i>c</i> represent the three throws. The result is obvious.</p> + +<hr style="width: 30%;" /> +<p><a name="X_387_THE_VILLAGE_CRICKET_MATCHa" id="X_387_THE_VILLAGE_CRICKET_MATCHa"></a><a href="#X_387_THE_VILLAGE_CRICKET_MATCH"><b>387.—THE VILLAGE CRICKET MATCH.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a387.png" width="400" height="325" alt="" title="" /> +</div> + +<p>The diagram No. 1 will show that as neither Mr. Podder nor Mr. Dumkins +can ever have been within the crease opposite to that from which he +started, Mr. Dumkins would score nothing by his performance. Diagram +No. 2 will, however, make it clear that since Mr. Luffey and Mr. +Struggles have, notwithstanding their energetic but careless +movements, contrived to change places, the manœuvre must increase Mr. +Struggles's total by one run.</p> + +<hr style="width: 30%;" /> +<p><a name="X_388_SLOW_CRICKETa" id="X_388_SLOW_CRICKETa"></a><a href="#X_388_SLOW_CRICKET"><b>388.—SLOW CRICKET.—<i>solution</i></b></a></p> + +<p>The captain must have been "not out" and scored 21. Thus:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>2 men (each lbw)</td><td align='right'>19</td></tr> +<tr><td align='left'>4 men (each caught)</td><td align='right'>17</td></tr> +<tr><td align='left'>1 man (run out)</td><td align='right'>0</td></tr> +<tr><td align='left'>3 men (each bowled)</td><td align='right'>9</td></tr> +<tr><td align='left'>1 man (captain—not out)</td><td align='right'>21</td></tr> +<tr><td align='left' class='bt'>11</td><td align='right' class='bt'>66</td></tr> +</table></div> + +<p>The captain thus scored exactly 15 more than the average of the team. +The "others" who were bowled could only refer to three men, as the +eleventh man would be "not out." The reader can discover for himself +why the captain must have been that eleventh man. It would not +necessarily follow with any figures.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 240<a name="Page_240" id="Page_240"></a></span><a name="X_389_THE_FOOTBALL_PLAYERSa" id="X_389_THE_FOOTBALL_PLAYERSa"></a><a href="#X_389_THE_FOOTBALL_PLAYERS"><b>389.—THE FOOTBALL PLAYERS.—<i>solution</i></b></a></p> + +<p>The smallest possible number of men is seven. They could be accounted +for in three different ways: 1. Two with both arms sound, one with +broken right arm, and four with both arms broken. 2. One with both +arms sound, one with broken left arm, two with broken right arm, and +three with both arms broken. 3. Two with left arm broken, three with +right arm broken, and two with both arms broken. But if every man was +injured, the last case is the only one that would apply.</p> + +<hr style="width: 30%;" /> +<p><a name="X_390_THE_HORSE-RACE_PUZZLEa" id="X_390_THE_HORSE-RACE_PUZZLEa"></a><a href="#X_390_THE_HORSE-RACE_PUZZLE"><b>390.—THE HORSE-RACE PUZZLE.—<i>solution</i></b></a></p> + +<p>The answer is: £12 on Acorn, £15 on Bluebottle, £20 on Capsule.</p> +<hr style="width: 30%;" /> +<p><a name="X_391_THE_MOTOR-CAR_RACEa" id="X_391_THE_MOTOR-CAR_RACEa"></a><a href="#X_391_THE_MOTOR-CAR_RACE"><b>391.—THE MOTOR-CAR RACE.—<i>solution</i></b></a></p> + +<p>The first point is to appreciate the fact that, in a race round a +circular track, there are the same number of cars behind one as there +are before. All the others are both behind and before. There were +thirteen cars in the race, including Gogglesmith's car. Then one-third +of twelve added to three-quarters of twelve will give us thirteen—the +correct answer.</p> + +<hr style="width: 30%;" /> +<p><a name="X_392_THE_PEBBLE_GAMEa" id="X_392_THE_PEBBLE_GAMEa"></a><a href="#X_392_THE_PEBBLE_GAME"><b>392.—THE PEBBLE GAME.—<i>solution</i></b></a></p> + +<p>In the case of fifteen pebbles, the first player wins if he first +takes two. Then when he holds an odd number and leaves 1, 8, or 9 he +wins, and when he holds an even number and leaves 4, 5, or 12 he also +wins. He can always do one or other of these things until the end of +the game, and so defeat his opponent. In the case of thirteen pebbles +the first player must lose if his opponent plays correctly. In fact, +the only numbers with which the first player ought to lose are 5 and +multiples of 8 added to 5, such as 13, 21, 29, etc.</p> + +<hr style="width: 30%;" /> +<p><a name="X_393_THE_TWO_ROOKSa" id="X_393_THE_TWO_ROOKSa"></a><a href="#X_393_THE_TWO_ROOKS"><b>393.—THE TWO ROOKS.—<i>solution</i></b></a></p> + +<p>The second player can always win, but to ensure his doing so he must +always place his rook, at the start and on every subsequent move, on +the same diagonal as his opponent's rook. He can then force his +opponent into a corner and win. Supposing the diagram to represent the +positions of the rooks at the start, then, if Black played first, +White might have placed his rook at A and won next move. Any square on +that diagonal from A to H will win, but the best play is always to +restrict the moves of the opposing rook as much as possible. If White +played first, then Black should have placed his rook at B (F would not +be so good, as it gives White more scope); then if White goes to C, +Black moves to D; White to E, Black to F; White to G, Black to C; +White to H, Black to I; and Black must win next move. If at any time +Black had failed to move on to the same diagonal as White, then White +could take Black's diagonal and win.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a393.png" width="400" height="400" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_394_PUSS_IN_THE_CORNERa" id="X_394_PUSS_IN_THE_CORNERa"></a><a href="#X_394_PUSS_IN_THE_CORNER"><b>394.—PUSS IN THE CORNER.—<i>solution</i></b></a></p> + +<p>No matter whether he plays first or second, the player A, who starts +the game at 55, must win. Assuming that B adopts the very best lines +of play in order to prolong as much as possible his existence, A, if +he has first move, can always on his 12th move capture B; and if he +has the second move, A can always on his 14th move make the capture. +His point is always to get diagonally in line with his opponent, and +by going to 33, if he has first move, he prevents B getting diagonally +in line with himself. Here are two good games. The number in front of +the hyphen is always A's move; that after the hyphen is B's:—</p> + +<p>33-8, 32-15, 31-22, 30-21, 29-14, 22-7, 15-6, 14-2, 7-3, 6-4, 11-, and +A must capture on his next (12th) move, -13, 54-20, 53-27, 52-34, +51-41, 50-34, 42-27, 35-20, 28-13, 21-6, 14-2, 7-3, 6-4, 11-, and A +must capture on his next (14th) move.</p> + +<hr style="width: 30%;" /> +<p><a name="X_395_A_WAR_PUZZLE_GAMEa" id="X_395_A_WAR_PUZZLE_GAMEa"></a><a href="#X_395_A_WAR_PUZZLE_GAME"><b>395.—A WAR PUZZLE GAME.—<i>solution</i></b></a></p> + +<p>The Britisher can always catch the enemy, no matter how clever and +elusive that astute individual may be; but curious though it may seem, +the British general can only do so after he has paid a somewhat +mysterious visit to the particular town marked "1" in the map, going +in by 3 and leaving by 2, or entering by 2 and leaving by 3. The three +towns that are shaded and have no numbers do not really come into the +question, as some may suppose, for the simple reason that the +Britisher never needs to enter any one of them, while the enemy cannot +be forced to go into them, and would be clearly ill-advised to do so +voluntarily. We may therefore leave these out of consideration +altogether. No matter what the enemy may do, the Britisher should make +the follow<span class='pagenum'>Pg 241<a name="Page_241" id="Page_241"></a></span>ing first nine moves: He should visit towns 24, 20, 19, +15, 11, 7, 3, 1, 2. If the enemy takes it into his head also to go to +town 1, it will be found that he will have to beat a precipitate +retreat <i>the same way that he went in</i>, or the Britisher will +infallibly catch him in towns 2 or 3, as the case may be. So the enemy +will be wise to avoid that north-west corner of the map altogether.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a395.png" width="400" height="396" alt="" title="" /> +</div> + +<p>Now, when the British general has made the nine moves that I have +given, the enemy will be, after his own ninth move, in one of the +towns marked 5, 8, 11, 13, 14, 16, 19, 21, 24, or 27. Of course, if he +imprudently goes to 3 or 6 at this point he will be caught at once. +Wherever he may happen to be, the Britisher "goes for him," and has no +longer any difficulty in catching him in eight more moves at most +(seventeen in all) in one of the following ways. The Britisher will +get to 8 when the enemy is at 5, and win next move; or he will get to +19 when the enemy is at 22, and win next move; or he will get to 24 +when the enemy is at 27, and so win next move. It will be found that +he can be forced into one or other of these fatal positions.</p> + +<p>In short, the strategy really amounts to this: the Britisher plays the +first nine moves that I have given, and although the enemy does his +very best to escape, our general goes after his antagonist and always +driving him away from that north-west corner ultimately closes in with +him, and wins. As I have said, the Britisher never need make more than +seventeen moves in all, and may win in fewer moves if the enemy plays +badly. But after playing those first nine moves it does not matter +even if the Britisher makes a few bad ones. He may lose time, but +cannot lose his advantage so long as he now keeps the enemy from town +1, and must eventually catch him.</p> + +<p>This is a complete explanation of the puzzle. It may seem a little +complex in print, but in practice the winning play will now be quite +easy to the reader. Make those nine moves, and there ought to be no +difficulty whatever in finding the concluding line of play. Indeed, it +might almost be said that then it is difficult for the British general +<i>not</i> to catch the enemy. It is a question of what in chess we call +the "opposition," and the visit by the Britisher to town 1 "gives him +the jump" on the enemy, as the man in the street would say.</p> + +<p>Here is an illustrative example in which the enemy avoids capture as +long as it is possible for him to do so. The Britisher's moves are +above the line and the enemy's below it. Play them alternately.</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right' class='bb'>24</td><td align='right' class='bb'>20</td><td align='right' class='bb'>19</td><td align='right' class='bb'>15</td><td align='right' class='bb'>11</td><td align='right' class='bb'>7</td><td align='right' class='bb'>3</td><td align='right' class='bb'>1</td><td align='right' class='bb'>2</td><td align='right' class='bb'>6</td><td align='right' class='bb'>10</td><td align='right' class='bb'>14</td><td align='right' class='bb'>18</td><td align='right' class='bb'>19</td><td align='right' class='bb'>20</td><td align='right' class='bb'>24</td></tr> +<tr><td align='right'>13</td><td align='right'>9</td><td align='right'>13</td><td align='right'>17</td><td align='right'>21</td><td align='right'>20</td><td align='right'>24</td><td align='right'>23</td><td align='right'>19</td><td align='right'>15</td><td align='right'>19</td><td align='right'>23</td><td align='right'>24</td><td align='right'>25</td><td align='right'>27</td></tr> +</table></div> + + +<p>The enemy must now go to 25 or B, in either of which towns he is +immediately captured.</p> + +<hr style="width: 30%;" /> +<p><a name="X_396_A_MATCH_MYSTERYa" id="X_396_A_MATCH_MYSTERYa"></a><a href="#X_396_A_MATCH_MYSTERY"><b>396.—A MATCH MYSTERY.—<i>solution</i></b></a></p> + +<p>If you form the three heaps (and are therefore the second to draw), +any one of the following thirteen groupings will give you a win if you +play correctly: 15, 14, 1; 15, 13, 2; 15, 12, 3; 15, 11, 4; 15, 10, 5; +15, 9, 6; 15, 8, 7; 14, 13, 3; 14, 11, 5; 14, 9, 7; 13, 11, 6; 13, 10, +7; 12, 11, 7.</p> + +<p>The beautiful general solution of this problem is as follows. Express +the number in every heap in powers of 2, avoiding repetitions and +remembering that 2<sup>0</sup> = 1. Then if you so leave the matches to your +opponent that there is an even number of every power, you can win. And +if at the start you leave the powers even, you can always continue to +do so throughout the game. Take, as example, the last grouping given +above—12, 11, 7. Expressed in powers of 2 we have—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>12</td><td align='center'>=</td><td align='center'>8</td><td align='center'>4</td><td align='center'>-</td><td align='center'>-</td></tr> +<tr><td align='right'>11</td><td align='center'>=</td><td align='center'>8</td><td align='center'>-</td><td align='center'>2</td><td align='center'>1</td></tr> +<tr><td align='right'>7</td><td align='center'>=</td><td align='center'>-</td><td align='center'>4</td><td align='center'>2</td><td align='center'>1</td></tr> +<tr><td align='right'></td><td></td><td align='center' class='bt'>2</td><td align='center' class='bt'>2</td><td align='center' class='bt'>2</td><td align='center' class='bt'>2</td></tr> +</table></div> + +<p>As there are thus two of every power, you must win. Say your opponent +takes 7 from the 12 heap. He then leaves—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>5</td><td align='center'>=</td><td align='center'>-</td><td align='center'>4</td><td align='center'>-</td><td align='center'>1</td></tr> +<tr><td align='right'>11</td><td align='center'>=</td><td align='center'>8</td><td align='center'>-</td><td align='center'>2</td><td align='center'>1</td></tr> +<tr><td align='right'>7</td><td align='center'>=</td><td align='center'>-</td><td align='center'>4</td><td align='center'>2</td><td align='center'>1</td></tr> +<tr><td align='right'></td><td></td><td align='center' class='bt'>1</td><td align='center' class='bt'>2</td><td align='center' class='bt'>2</td><td align='center' class='bt'>3</td></tr> +</table></div> + +<p>Here the powers are not all even in number, but by taking 9 from the +11 heap you immediately restore your winning position, thus—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>5</td><td align='center'>=</td><td align='center'>-</td><td align='center'>4</td><td align='center'>-</td><td align='center'>1</td></tr> +<tr><td align='right'>2</td><td align='center'>=</td><td align='center'>-</td><td align='center'>-</td><td align='center'>2</td><td align='center'>-</td></tr> +<tr><td align='right'>7</td><td align='center'>=</td><td align='center'>-</td><td align='center'>4</td><td align='center'>2</td><td align='center'>1</td></tr> +<tr><td align='right'></td><td></td><td align='center' class='bt'>-</td><td align='center' class='bt'>2</td><td align='center' class='bt'>2</td><td align='center' class='bt'>2</td></tr> +</table></div> + +<p>And so on to the end. This solution is quite <span class='pagenum'>Pg 242<a name="Page_242" id="Page_242"></a></span>general, and applies to +any number of matches and any number of heaps. A correspondent informs +me that this puzzle game was first propounded by Mr. W.M.F. Mellor, +but when or where it was published I have not been able to ascertain.</p> + +<hr style="width: 30%;" /> +<p><a name="X_397_THE_MONTENEGRIN_DICE_GAMEa" id="X_397_THE_MONTENEGRIN_DICE_GAMEa"></a><a href="#X_397_THE_MONTENEGRIN_DICE_GAME"><b>397.—THE MONTENEGRIN DICE GAME.—<i>solution</i></b></a></p> + +<p>The players should select the pairs 5 and 9, and 13 and 15, if the +chances of winning are to be quite equal. There are 216 different ways +in which the three dice may fall. They may add up 5 in 6 different +ways and 9 in 25 different ways, making 31 chances out of 216 for the +player who selects these numbers. Also the dice may add up 13 in 21 +different ways, and 15 in 10 different ways, thus giving the other +player also 31 chances in 216.</p> + +<hr style="width: 30%;" /> +<p><a name="X_398_THE_CIGAR_PUZZLEa" id="X_398_THE_CIGAR_PUZZLEa"></a><a href="#X_398_THE_CIGAR_PUZZLE"><b>398.—THE CIGAR PUZZLE.—<i>solution</i></b></a></p> + +<p>Not a single member of the club mastered this puzzle, and yet I shall +show that it is so simple that the merest child can understand its +solution—when it is pointed out to him! The large majority of my +friends expressed their entire bewilderment. Many considered that "the +theoretical result, in any case, is determined by the relationship +between the table and the cigars;" others, regarding it as a problem +in the theory of Probabilities, arrived at the conclusion that the +chances are slightly in favour of the first or second player, as the +case may be. One man took a table and a cigar of particular +dimensions, divided the table into equal sections, and proceeded to +make the two players fill up these sections so that the second player +should win. But why should the first player be so accommodating? At +any stage he has only to throw down a cigar obliquely across several +of these sections entirely to upset Mr. 2's calculations! We have to +assume that each player plays the best possible; not that one +accommodates the other.</p> + +<p>The theories of some other friends would be quite sound if the shape +of the cigar were that of a torpedo—perfectly symmetrical and pointed +at both ends.</p> + +<p>I will show that the first player should infallibly win, if he always +plays in the best possible manner. Examine carefully the following +diagram, No. 1, and all will be clear.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a398.png" width="400" height="208" alt="" title="" /> +</div> + +<p>The first player must place his first cigar <i>on end</i> in the exact +centre of the table, as indicated by the little circle. Now, whatever +the second player may do throughout, the first player must always +repeat it in an exactly diametrically opposite position. Thus, if the +second player places a cigar at A, I put one at AA; he places one at +B, I put one at BB; he places one at C, I put one at CC; he places one +at D, I put one at DD; he places one at E, I put one at EE; and so on +until no more cigars can be placed without touching. As the cigars are +supposed to be exactly alike in every respect, it is perfectly clear +that for every move that the second player may choose to make, it is +possible exactly to repeat it on a line drawn through the centre of +the table. The second player can always duplicate the first player's +move, no matter where he may place a cigar, or whether he places it on +end or on its side. As the cigars are all alike in every respect, one +will obviously balance over the edge of the table at precisely the +same point as another. Of course, as each player is supposed to play +in the best possible manner, it becomes a matter of theory. It is no +valid objection to say that in actual practice one would not be +sufficiently exact to be sure of winning. If as the first player you +did not win, it would be in consequence of your <i>not</i> having played +the best possible.</p> + +<p>The second diagram will serve to show why the first cigar must be +placed on end. (And here I will say that the first cigar that I +selected from a box I was able so to stand on end, and I am allowed to +assume that all the other cigars would do the same.) If the first +cigar were placed on its side, as at F, then the second player could +place a cigar as at G—as near as possible, but not actually touching +F. Now, in this position you cannot repeat his play on the opposite +side, because the two ends of the cigar are not alike. It will be seen +that GG, when placed on the opposite side in the same relation to the +centre, intersects, or lies on top of, F, whereas the cigars are not +allowed to touch. You must therefore put the cigar farther away from +the centre, which would result in your having insufficient room +between the centre and the bottom left-hand corner to repeat +everything that the other player would do between G and the top +right-hand corner. Therefore the result would not be a certain win for +the first player.</p> + +<hr style="width: 30%;" /> +<p><a name="X_399_THE_TROUBLESOME_EIGHTa" id="X_399_THE_TROUBLESOME_EIGHTa"></a><a href="#X_399_THE_TROUBLESOME_EIGHT"><b>399.—THE TROUBLESOME EIGHT.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a399.png" width="400" height="407" alt="" title="" /> +</div> + +<p>The conditions were to place a different number in each of the nine +cells so that the three rows, <span class='pagenum'>Pg 243<a name="Page_243" id="Page_243"></a></span>three columns, and two diagonals should +each add up 15. Probably the reader at first set himself an impossible +task through reading into these conditions something which is not +there—a common error in puzzle-solving. If I had said "a different +figure," instead of "a different number," it would have been quite +impossible with the 8 placed anywhere but in a corner. And it would +have been equally impossible if I had said "a different whole number." +But a number may, of course, be fractional, and therein lies the +secret of the puzzle. The arrangement shown in the figure will be +found to comply exactly with the conditions: all the numbers are +different, and the square adds up 15 in all the required eight ways.</p> + +<hr style="width: 30%;" /> +<p><a name="X_400_THE_MAGIC_STRIPSa" id="X_400_THE_MAGIC_STRIPSa"></a><a href="#X_400_THE_MAGIC_STRIPS"><b>400.—THE MAGIC STRIPS.—<i>solution</i></b></a></p> + +<p>There are of course six different places between the seven figures in +which a cut may be made, and the secret lies in keeping one strip +intact and cutting each of the other six in a different place. After +the cuts have been made there are a large number of ways in which the +thirteen pieces may be placed together so as to form a magic square. +Here is one of them:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a400.png" width="400" height="387" alt="" title="" /> +</div> + +<p>The arrangement has some rather interesting features. It will be seen +that the uncut strip is at the top, but it will be found that if the +bottom row of figures be placed at the top the numbers will still form +a magic square, and that every successive removal from the bottom to +the top (carrying the uncut strip stage by stage to the bottom) will +produce the same result. If we imagine the numbers to be on seven +complete <i>perpendicular</i> strips, it will be found that these columns +could also be moved in succession from left to right or from right to +left, each time producing a magic square.</p> + +<hr style="width: 30%;" /> +<p><a name="X_401_EIGHT_JOLLY_GAOL_BIRDSa" id="X_401_EIGHT_JOLLY_GAOL_BIRDSa"></a><a href="#X_401_EIGHT_JOLLY_GAOL_BIRDS"><b>401.—EIGHT JOLLY GAOL BIRDS.—<i>solution</i></b></a></p> + +<p>There are eight ways of forming the magic square—all merely different +aspects of one fundamental arrangement. Thus, if you give our first +square a quarter turn you will get the second square; and as the four +sides may be in turn brought to the top, there are four aspects. These +four in turn reflected in a mirror produce the remaining four aspects. +Now, of these eight arrangements only four can possibly be reached +under the conditions, and only two of these four can be reached in the +fewest possible moves, which is nineteen. These two arrangements are +shown. Move the men in the following order: 5, 3, 2, 5, 7, 6, 4, 1, 5, +7, 6, 4, 1, 6, 4, 8, 3, 2, 7, and you get the first square. Move them +thus: 4, 1, 2, 4, 1, 6, 7, 1, 5, 8, 1, 5, 6, 7, 5, 6, 4, 2, 7, and you +have the arrangement in the second square. In the first case every man +has moved, but in the second case the man numbered 3 has never left +his cell. Therefore No. 3 must be the obstinate prisoner, and the +second square must be the required arrangement.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a401.png" width="400" height="176" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_402_NINE_JOLLY_GAOL_BIRDSa" id="X_402_NINE_JOLLY_GAOL_BIRDSa"></a><a href="#X_402_NINE_JOLLY_GAOL_BIRDS"><b>402.—NINE JOLLY GAOL BIRDS.—<i>solution</i></b></a></p> + +<p>There is a pitfall set for the unwary in this little puzzle. At the +start one man is allowed to be placed on the shoulders of another, so +as to give always one empty cell to enable the prisoners to move about +without any two ever being in a cell together. The two united +prisoners are allowed to add their numbers together, and are, of +course, permitted to remain together at the completion of the magic +square. But they are obviously not compelled so to remain together, +provided that one of the pair on his final move does not break the +condition of entering a cell already occupied. After the acute solver +has noticed this point, it is for him to determine which method is the +better one—for the two to be together at the count or to separate. As +a matter of fact, the puzzle can be solved in seventeen moves if the +men are to remain together; but if they separate at the<span class='pagenum'>Pg 244<a name="Page_244" id="Page_244"></a></span> +end, they may actually save a move and perform the feat in sixteen! +The trick consists in placing the man in the centre on the back of one +of the corner men, and then working the pair into the centre before +their final separation.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a402.png" width="400" height="227" alt="" title="" /> +</div> + +<p>Here are the moves for getting the men into one or other of the above +two positions. The numbers are those of the men in the order in which +they move into the cell that is for the time being vacant. The pair is +shown in brackets:—</p> + +<p>Place 5 on 1. Then, 6, 9, 8, 6, 4, (6), 2, 4, 9, 3, 4, 9, (6), 7, 6, +1.</p> + +<p>Place 5 on 9. Then, 4, 1, 2, 4, 6, (14), 8, 6, 1, 7, 6, 1, (14), 3, 4, +9.</p> + +<p>Place 5 on 3. Then, 6, (8), 2, 6, 4, 7, 8, 4, 7, 1, 6, 7, (8), 9, 4, +3.</p> + +<p>Place 5 on 7. Then, 4, (12), 8, 4, 6, 3, 2, 6, 3, 9, 4, 3, (12), 1, 6, +7.</p> + +<p>The first and second solutions produce Diagram A; the second and third +produce Diagram B. There are only sixteen moves in every case. Having +found the fewest moves, we had to consider how we were to make the +burdened man do as little work as possible. It will at once be seen +that as the pair have to go into the centre before separating they +must take at fewest two moves. The labour of the burdened man can only +be reduced by adopting the other method of solution, which, however, +forces us to take another move.</p> + +<hr style="width: 30%;" /> +<p><a name="X_403_THE_SPANISH_DUNGEONa" id="X_403_THE_SPANISH_DUNGEONa"></a><a href="#X_403_THE_SPANISH_DUNGEON"><b>403.—THE SPANISH DUNGEON.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a403.png" width="400" height="183" alt="" title="" /> +</div> + +<p>This can best be solved by working backwards—that is to say, you must +first catch your square, and then work back to the original position. +We must first construct those squares which are found to require the +least amount of readjustment of the numbers. Many of these we know +cannot possibly be reached. When we have before us the most favourable +possible arrangements, it then becomes a question of careful analysis +to discover which position can be reached in the fewest moves. I am +afraid, however, it is only after considerable study and experience +that the solver is able to get such a grasp of the various "areas of +disturbance" and methods of circulation that his judgment is of much +value to him.</p> + +<p>The second diagram is a most favourable magic square position. It will +be seen that prisoners 4, 8, 13, and 14 are left in their original +cells. This position may be reached in as few as thirty-seven moves. +Here are the moves: 15, 14, 10, 6, 7, 3, 2, 7, 6, 11, 3, 2, 7, 6, 11, +10, 14, 3, 2, 11, 10, 9, 5, 1, 6, 10, 9, 5, 1, 6, 10, 9, 5, 2, 12, 15, +3. This short solution will probably surprise many readers who may not +find a way under from sixty to a hundred moves. The clever prisoner +was No. 6, who in the original illustration will be seen with his arms +extended calling out the moves. He and No. 10 did most of the work, +each changing his cell five times. No. 12, the man with the crooked +leg, was lame, and therefore fortunately had only to pass from his +cell into the next one when his time came round.</p> + +<hr style="width: 30%;" /> +<p><a name="X_404_THE_SIBERIAN_DUNGEONSa" id="X_404_THE_SIBERIAN_DUNGEONSa"></a><a href="#X_404_THE_SIBERIAN_DUNGEONS"><b>404.—THE SIBERIAN DUNGEONS.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a404.png" width="400" height="389" alt="" title="" /> +</div> + +<p>In attempting to solve this puzzle it is clearly necessary to seek +such magic squares as seem the most favourable for our purpose, and +then carefully examine and try them for "fewest moves." Of course it +at once occurs to us that if we can adopt a square in which a certain +number of men need not leave their original cells, we may save moves +on the one hand, but we may obstruct our movements on the other. For +example, a magic square may be formed with the 6, 7, 13, and 16 +unmoved; but in such case it is obvious that a solution is impossible, +since cells 14 and 15 can neither be left nor entered without breaking +the condition of no two men ever being in the same cell together.</p> + +<p>The following solution in fourteen moves was found by Mr. G. +Wotherspoon: 8-17, 16-21, 6-16, 14-8, 5-18, 4-14, 3-24, 11-20, 10-19, +2-23, 13-22, 12-6, 1-5, 9-13. As this solution is in what I consider +the theoretical minimum number of moves, I am confident that it cannot +be improved upon, and on this point Mr. Wotherspoon is of the same +opinion.</p> + +<hr style="width: 30%;" /> +<p><a name="X_405_CARD_MAGIC_SQUARESa" id="X_405_CARD_MAGIC_SQUARESa"></a><a href="#X_405_CARD_MAGIC_SQUARES"><b>405.—CARD MAGIC SQUARES.—<i>solution</i></b></a></p> + +<p>Arrange the cards as follows for the three new squares:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>3</td><td align='right'>2</td><td align='right'>4</td></tr> +<tr><td align='right'>4</td><td align='right'>3</td><td align='right'>2</td></tr> +<tr><td align='right'>2</td><td align='right'>4</td><td align='right'>3</td></tr> +</table></div> +<p><br /></p> +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>6</td><td align='right'>5</td><td align='right'>7</td></tr> +<tr><td align='right'>7</td><td align='right'>6</td><td align='right'>5</td></tr> +<tr><td align='right'>5</td><td align='right'>7</td><td align='right'>6</td></tr> +</table></div> +<p><br /></p> +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>9</td><td align='right'>8</td><td align='right'>10</td></tr> +<tr><td align='right'>10</td><td align='right'>9</td><td align='right'>8</td></tr> +<tr><td align='right'>8</td><td align='right'>10</td><td align='right'>9</td></tr> +</table></div> + +<p>Three aces and one ten are not used. The summations of the four +squares are thus: 9, 15, 18, and 27—all different, as required.</p> + +<hr style="width: 30%;" /> +<p><span class='pagenum'>Pg 245<a name="Page_245" id="Page_245"></a></span><a name="X_406_THE_EIGHTEEN_DOMINOESa" id="X_406_THE_EIGHTEEN_DOMINOESa"></a><a href="#X_406_THE_EIGHTEEN_DOMINOES"><b>406.—THE EIGHTEEN DOMINOES.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a406.png" width="400" height="401" alt="" title="" /> +</div> + +<p>The illustration explains itself. It will be found that the pips in +every column, row, and long diagonal add up 18, as required.</p> + +<hr style="width: 30%;" /> +<p><a name="X_407_TWO_NEW_MAGIC_SQUARESa" id="X_407_TWO_NEW_MAGIC_SQUARESa"></a><a href="#X_407_TWO_NEW_MAGIC_SQUARES"><b>407.—TWO NEW MAGIC SQUARES.—<i>solution</i></b></a></p> + +<p>Here are two solutions that fulfil the conditions:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a407.png" width="400" height="208" alt="" title="" /> +</div> + +<p>The first, by subtracting, has a constant 8, and the associated pairs +all have a difference of 4. The second square, by dividing, has a +constant 9, and all the associated pairs produce 3 by division. These +are two remarkable and instructive squares.</p> + +<hr style="width: 30%;" /> +<p><a name="X_408_MAGIC_SQUARES_OF_TWO_DEGREESa" id="X_408_MAGIC_SQUARES_OF_TWO_DEGREESa"></a><a href="#X_408_MAGIC_SQUARES_OF_TWO_DEGREES"><b>408.—MAGIC SQUARES OF TWO DEGREES.—<i>solution</i></b></a></p> + +<p>The following is the square that I constructed. As it stands the +constant is 260. If for every number you substitute, in its allotted +place, its square, then the constant will be 11,180. Readers can write +out for themselves the second degree square.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a408.png" width="400" height="398" alt="" title="" /> +</div> + +<p>The main key to the solution is the pretty law that if eight numbers +sum to 260 and their squares to 11,180, then the same will happen in +the case of the eight numbers that are complementary to 65. Thus 1 + +18 + 23 + 26 + 31 + 48 + 56 + 57 = 260, and the sum of their squares +is 11,180. Therefore 64 + 47 + 42 + 39 + 34 + 17 + 9 + 8 (obtained by +subtracting each of the above numbers from 65) will sum to 260 and +their squares to 11,180. Note that in every one of the sixteen smaller +squares the two diagonals sum to 65. There are four columns and four +rows with their complementary columns and rows. Let us pick out the +numbers found in the 2nd, 1st, 4th, and 3rd rows and arrange them thus +:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'>1</td><td align='right'>8</td><td align='right'>28</td><td align='right'>29</td><td align='right'>42</td><td align='right'>47</td><td align='right'>51</td><td align='right'>54</td></tr> +<tr><td align='right'>2</td><td align='right'>7</td><td align='right'>27</td><td align='right'>30</td><td align='right'>41</td><td align='right'>48</td><td align='right'>52</td><td align='right'>53</td></tr> +<tr><td align='right'>3</td><td align='right'>6</td><td align='right'>26</td><td align='right'>31</td><td align='right'>44</td><td align='right'>45</td><td align='right'>49</td><td align='right'>56</td></tr> +<tr><td align='right'>4</td><td align='right'>5</td><td align='right'>25</td><td align='right'>32</td><td align='right'>43</td><td align='right'>46</td><td align='right'>50</td><td align='right'>55</td></tr> +</table></div> + +<p>Here each column contains four consecutive numbers cyclically +arranged, four running in one direction and four in the other. The +numbers in the 2nd, 5th, 3rd, and 8th columns of the square may be +similarly grouped. The great difficulty lies in discovering the +conditions governing these groups of numbers, the pairing of the +complementaries in the squares of four and the formation of the +diagonals. But when a correct solution is shown, as above, it +discloses all the more important keys to the mystery. I am inclined to +think this square of two degrees the most elegant thing that exists in +magics. I believe such a magic square cannot be constructed in the +case of any order lower than 8.</p> + +<hr style="width: 30%;" /> +<p><a name="X_409_THE_BASKETS_OF_PLUMSa" id="X_409_THE_BASKETS_OF_PLUMSa"></a><a href="#X_409_THE_BASKETS_OF_PLUMS"><b>409.—THE BASKETS OF PLUMS.—<i>solution</i></b></a></p> + +<p>As the merchant told his man to distribute the contents of one of the +baskets of plums "among some children," it would not be permissible to +give the complete basketful to one child; and as it was also directed +that the man was to give "plums to every child, so that each should +receive an equal number," it would also not be allowed to select just +as many children as there were plums in a basket and give each child a +single plum. Consequently, if the number of <span class='pagenum'>Pg 246<a name="Page_246" id="Page_246"></a></span>plums in every basket was +a prime number, then the man would be correct in saying that the +proposed distribution was quite impossible. Our puzzle, therefore, +resolves itself into forming a magic square with nine different prime +numbers.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a409.png" width="400" height="428" alt="" title="" /> +</div> + +<p>In Diagram A we have a magic square in prime numbers, and it is the +one giving the smallest constant sum that is possible. As to the +little trap I mentioned, it is clear that Diagram A is barred out by +the words "every basket contained plums," for one plum is not plums. +And as we were referred to the baskets, "as shown in the +illustration," it is perfectly evident, without actually attempting to +count the plums, that there are at any rate more than 7 plums in every +basket. Therefore C is also, strictly speaking, barred. Numbers over +20 and under, say, 250 would certainly come well within the range of +possibility, and a large number of arrangements would come within +these limits. Diagram B is one of them. Of course we can allow for the +false bottoms that are so frequently used in the baskets of +fruitsellers to make the basket appear to contain more fruit than it +really does.</p> + +<p>Several correspondents assumed (on what grounds I cannot think) that +in the case of this problem the numbers cannot be in consecutive +arithmetical progression, so I give Diagram D to show that they were +mistaken. The numbers are 199, 409, 619, 829, 1,039, 1,249, 1,459, +1,669, and 1,879—all primes with a common difference of 210.</p> + +<hr style="width: 30%;" /> +<p><a name="X_410_THE_MANDARINS_T_PUZZLEa" id="X_410_THE_MANDARINS_T_PUZZLEa"></a><a href="#X_410_THE_MANDARINS_T_PUZZLE"><b>410.—THE MANDARIN'S "T" PUZZLE.—<i>solution</i></b></a></p> + +<p>There are many different ways of arranging the numbers, and either the +2 or the 3 may be omitted from the "T" enclosure. The arrangement that +I give is a "nasik" square. Out of the total of 28,800 nasik squares +of the fifth order this is the only one (with its one reflection) that +fulfils the "T" condition. This puzzle was suggested to me by Dr. C. +Planck.</p> + + +<div class="figcenter" style="width: 400px;"> +<img src="images/a410.png" width="400" height="400" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_411_A_MAGIC_SQUARE_OF_COMPOSITESa" id="X_411_A_MAGIC_SQUARE_OF_COMPOSITESa"></a><a href="#X_411_A_MAGIC_SQUARE_OF_COMPOSITES"><b>411.—A MAGIC SQUARE OF COMPOSITES.—<i>solution</i></b></a></p> + +<p>The problem really amounts to finding the smallest prime such that the +next higher prime shall exceed it by 10 at least. If we write out a +little list of primes, we shall not need to exceed 150 to discover +what we require, for after 113 the next prime is 127. We can then form +the square in the diagram, where every number is composite. This is +the solution in the smallest numbers. We thus see that the answer is +arrived at quite easily, in a square of the third order, by trial. But +I propose to show how we may get an answer (not, it is true, the one +in smallest numbers) without any tables or trials, but in a very +direct and rapid manner.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a411.png" width="400" height="404" alt="" title="" /> +</div> + +<p>First write down any consecutive numbers, the smallest being greater +than 1—say, 2, 3, 4, 5, 6, 7, 8, 9, 10. The only factors in these +numbers are 2, 3, 5, and 7. We therefore mul<span class='pagenum'>Pg 247<a name="Page_247" id="Page_247"></a></span>tiply these four numbers +together and add the product, 210, to each of the nine numbers. The +result is the nine consecutive composite numbers, 212 to 220 +inclusive, with which we can form the required square. Every number +will necessarily be divisible by its difference from 210. It will be +very obvious that by this method we may find as many consecutive +composites as ever we please. Suppose, for example, we wish to form a +magic square of sixteen such numbers; then the numbers 2 to 17 contain +the factors 2, 3, 5, 7, 11, 13, and 17, which, multiplied together, +make 510510 to be added to produce the sixteen numbers 510512 to +510527 inclusive, all of which are composite as before.</p> + +<p>But, as I have said, these are not the answers in the smallest +numbers: for if we add 523 to the numbers 1 to 16, we get sixteen +consecutive composites; and if we add 1,327 to the numbers 1 to 25, we +get twenty-five consecutive composites, in each case the smallest +numbers possible. Yet if we required to form a magic square of a +hundred such numbers, we should find it a big task by means of tables, +though by the process I have shown it is quite a simple matter. Even +to find thirty-six such numbers you will search the tables up to +10,000 without success, and the difficulty increases in an +accelerating ratio with each square of a larger order.</p> + +<hr style="width: 30%;" /> +<p><a name="X_412_THE_MAGIC_KNIGHTS_TOURa" id="X_412_THE_MAGIC_KNIGHTS_TOURa"></a><a href="#X_412_THE_MAGIC_KNIGHTS_TOUR"><b>412.—THE MAGIC KNIGHT'S TOUR.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a412.png" width="400" height="394" alt="" title="" /> +</div> + +<p>Here each successive number (in numerical order) is a knight's move +from the preceding number, and as 64 is a knight's move from 1, the +tour is "re-entrant." All the columns and rows add up 260. +Unfortunately, it is not a perfect magic square, because the diagonals +are incorrect, one adding up 264 and the other 256—requiring only the +transfer of 4 from one diagonal to the other. I think this is the best +result that has ever been obtained (either re-entrant or not), and +nobody can yet say whether a perfect solution is possible or +impossible.</p> + +<hr style="width: 30%;" /> +<p><a name="X_413_A_CHESSBOARD_FALLACYa" id="X_413_A_CHESSBOARD_FALLACYa"></a><a href="#X_413_A_CHESSBOARD_FALLACY"><b>413.—A CHESSBOARD FALLACY.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a413.png" width="400" height="240" alt="" title="" /> +</div> + +<p>The explanation of this little fallacy is as follows. The error lies +in assuming that the little triangular piece, marked C, is exactly the +same height as one of the little squares of the board. As a matter of +fact, its height (if we make the sixty-four squares each a square +inch) will be 1<sup>1</sup>/<sub>7</sub> in. Consequently the rectangle is really 9<sup>1</sup>/<sub>7</sub> in. +by 7 in., so that the area is sixty-four square inches in either case. +Now, although the pieces do fit together exactly to form the perfect +rectangle, yet the directions of the horizontal lines in the pieces +will not coincide. The new diagram above will make everything quite +clear to the reader.</p> + +<hr style="width: 30%;" /> +<p><a name="X_414_WHO_WAS_FIRSTa" id="X_414_WHO_WAS_FIRSTa"></a><a href="#X_414_WHO_WAS_FIRST"><b>414.—WHO WAS FIRST?—<i>solution</i></b></a></p> + +<p>Biggs, who saw the smoke, would be first; Carpenter, who saw the +bullet strike the water, would be second; and Anderson, who heard the +report, would be last of all.</p> + +<hr style="width: 30%;" /> +<p><a name="X_415_A_WONDERFUL_VILLAGEa" id="X_415_A_WONDERFUL_VILLAGEa"></a><a href="#X_415_A_WONDERFUL_VILLAGE"><b>415.—A WONDERFUL VILLAGE.—<i>solution</i></b></a></p> + +<p>When the sun is in the horizon of any place (whether in Japan or +elsewhere), he is the length of half the earth's diameter more distant +from that place than in his meridian at noon. As the earth's +semi-diameter is nearly 4,000 miles, the sun must be considerably more +than 3,000 miles nearer at noon than at his rising, there being no +valley even the hundredth part of 1,000 miles deep.</p> + +<hr style="width: 30%;" /> +<p><a name="X_416_A_CALENDAR_PUZZLEa" id="X_416_A_CALENDAR_PUZZLEa"></a><a href="#X_416_A_CALENDAR_PUZZLE"><b>416.—A CALENDAR PUZZLE.—<i>solution</i></b></a></p> + +<p>The first day of a century can never fall on a Sunday; nor on a +Wednesday or a Friday.</p> + +<hr style="width: 30%;" /> +<p><a name="X_417_THE_TIRING_IRONSa" id="X_417_THE_TIRING_IRONSa"></a><a href="#X_417_THE_TIRING_IRONS"><b>417.—THE TIRING IRONS.—<i>solution</i></b></a></p> + +<p>I will give my complete working of the solution, so that readers may +see how easy it is when you know how to proceed. And first of all, as +there is an even number of rings, I will say that they may all be +taken off in one-third of (2<sup>(n + 1)</sup> - 2) moves; and since <i>n</i> in our +case is 14, all the rings may be taken off in 10,922 moves. Then I say +10,922 - 9,999 = 923, and proceed to find the position when only 923 +out of the 10,922 moves remain to be made. Here is the curious method +of doing this. It is based on <span class='pagenum'>Pg 248<a name="Page_248" id="Page_248"></a></span>the binary scale method used by +Monsieur L. Gros, for an account of which see W.W. Rouse Ball's +<i>Mathematical Recreations</i>.</p> + +<p>Divide 923 by 2, and we get 461 and the remainder 1; divide 461 by 2, +and we get 230 and the remainder 1; divide 230 by 2, and we get 115 +and the remainder nought. Keep on dividing by 2 in this way as long as +possible, and all the remainders will be found to be 1, 1, 1, 0, 0, 1, +1, 0, 1, 1, the last remainder being to the left and the first +remainder to the right. As there are fourteen rings and only ten +figures, we place the difference, in the form of four noughts, in +brackets to the left, and bracket all those figures that repeat a +figure on their left. Then we get the following arrangement: (0 0 0 0) 1 +(1 1) 0 (0) 1 (1) 0 1 (1). This is the correct answer to the puzzle, for +if we now place rings below the line to represent the figures in +brackets and rings on the line for the other figures, we get the +solution in the required form, as below:—</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a417.png" width="400" height="65" alt="" title="" /> +</div> + +<p>This is the exact position of the rings after the 9,999th move has +been made, and the reader will find that the method shown will solve +any similar question, no matter how many rings are on the +tiring-irons. But in working the inverse process, where you are +required to ascertain the number of moves necessary in order to reach +a given position of the rings, the rule will require a little +modification, because it does not necessarily follow that the position +is one that is actually reached in course of taking off all the rings +on the irons, as the reader will presently see. I will here state that +where the total number of rings is odd the number of moves required to +take them all off is one-third of (2<sup>(<i>n</i> + 1)</sup> - 1).</p> + +<p>With <i>n</i> rings (where <i>n</i> is <i>odd</i>) there are 2<sup><i>n</i></sup> positions counting +all on and all off. In <sup>1</sup>/<sub>3</sub> (2<sup>(n+1)</sup> + 2) positions they are all +removed. The number of positions not used is (<sup>1</sup>/<sub>3</sub>)(2<sup><i>n</i></sup> - 2).</p> + +<p>With <i>n</i> rings (where <i>n</i> is <i>even</i>) there are 2<sup>n</sup> positions counting +all on and all off. In (2<sup>(<i>n</i> + 1)</sup> + 1) positions they are all removed. +The number of positions not used is here (<sup>1</sup>/<sub>3</sub>)(2<sup><i>n</i></sup> - 1).</p> + +<p>It will be convenient to tabulate a few cases.</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center' class='bb'>No. of <br />Rings.</td><td align='center' class='bb'>Total <br />Positions.</td><td align='center' class='bb'>Positions <br />used.</td><td align='center' class='bb'>Positions <br />not used.</td></tr> +<tr><td align='right'>1</td><td align='right'>2</td><td align='right'>2</td><td align='right'>0</td></tr> +<tr><td align='right'>3</td><td align='right'>8</td><td align='right'>6</td><td align='right'>2</td></tr> +<tr><td align='right'>5</td><td align='right'>32</td><td align='right'>22</td><td align='right'>10</td></tr> +<tr><td align='right'>7</td><td align='right'>128</td><td align='right'>86</td><td align='right'>42</td></tr> +<tr><td align='right'>9</td><td align='right'>512</td><td align='right'>342</td><td align='right'>170</td></tr> +<tr><td> </td></tr> +<tr><td align='right'>2</td><td align='right'>4</td><td align='right'>3</td><td align='right'>1</td></tr> +<tr><td align='right'>4</td><td align='right'>16</td><td align='right'>11</td><td align='right'>5</td></tr> +<tr><td align='right'>6</td><td align='right'>64</td><td align='right'>43</td><td align='right'>21</td></tr> +<tr><td align='right'>8</td><td align='right'>256</td><td align='right'>171</td><td align='right'>85</td></tr> +<tr><td align='right'>10</td><td align='right'>1024</td><td align='right'>683</td><td align='right'>341</td></tr> +</table></div> + +<p>Note first that the number of <i>positions used</i> is one more than the +number of <i>moves</i> required to take all the rings off, because we are +including "all on" which is a position but not a move. Then note that +the number of <i>positions not used</i> is the same as the number of <i>moves +used</i> to take off a set that has one ring fewer. For example, it takes +85 moves to remove 7 rings, and the 42 positions not used are exactly +the number of moves required to take off a set of 6 rings. The fact is +that if there are 7 rings and you take off the first 6, and then wish +to remove the 7th ring, there is no course open to you but to reverse +all those 42 moves that never ought to have been made. In other words, +you must replace all the 7 rings on the loop and start afresh! You +ought first to have taken off 5 rings, to do which you should have +taken off 3 rings, and previously to that 1 ring. To take off 6 you +first remove 2 and then 4 rings.</p> + +<hr style="width: 30%;" /> +<p><a name="X_418_SUCH_A_GETTING_UPSTAIRSa" id="X_418_SUCH_A_GETTING_UPSTAIRSa"></a><a href="#X_418_SUCH_A_GETTING_UPSTAIRS"><b>418.—SUCH A GETTING UPSTAIRS.—<i>solution</i></b></a></p> + +<p>Number the treads in regular order upwards, 1 to 8. Then proceed as +follows: 1 (step back to floor), 1, 2, 3 (2), 3, 4, 5 (4), 5, 6, 7 +(6), 7, 8, landing (8), landing. The steps in brackets are taken in a +backward direction. It will thus be seen that by returning to the +floor after the first step, and then always going three steps forward +for one step backward, we perform the required feat in nineteen steps.</p> + +<hr style="width: 30%;" /> +<p><a name="X_419_THE_FIVE_PENNIESa" id="X_419_THE_FIVE_PENNIESa"></a><a href="#X_419_THE_FIVE_PENNIES"><b>419.—THE FIVE PENNIES.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a419.png" width="400" height="349" alt="" title="" /> +</div> + +<p>First lay three of the pennies in the way shown in Fig. 1. Now hold +the remaining two pennies in the position shown in Fig. 2, so that +they touch one another at the top, and at the base are in contact with +the three horizontally placed coins. Then the five pennies will be +equidistant, for every penny will touch every other penny.</p> + +<hr style="width: 30%;" /> +<p><a name="X_420_THE_INDUSTRIOUS_BOOKWORMa" id="X_420_THE_INDUSTRIOUS_BOOKWORMa"></a><a href="#X_420_THE_INDUSTRIOUS_BOOKWORM"><b>420.—THE INDUSTRIOUS BOOKWORM.—<i>solution</i></b></a></p> + +<p>The hasty reader will assume that the bookworm, in boring from the +first to the last page <span class='pagenum'>Pg 249<a name="Page_249" id="Page_249"></a></span>of a book in three volumes, standing in their +proper order on the shelves, has to go through all three volumes and +four covers. This, in our case, would mean a distance of 9½ in., +which is a long way from the correct answer. You will find, on +examining any three consecutive volumes on your shelves, that the +first page of Vol. I. and the last page of Vol. III. are actually the +pages that are nearest to Vol. II., so that the worm would only have +to penetrate four covers (together, ½ in.) and the leaves in the +second volume (3 in.), or a distance of 3½ inches, in order to +tunnel from the first page to the last.</p> + +<hr style="width: 30%;" /> +<p><a name="X_421_A_CHAIN_PUZZLEa" id="X_421_A_CHAIN_PUZZLEa"></a><a href="#X_421_A_CHAIN_PUZZLE"><b>421.—A CHAIN PUZZLE.—<i>solution</i></b></a></p> + +<p>To open and rejoin a link costs threepence. Therefore to join the nine +pieces into an endless chain would cost 2<i>s</i>. 3<i>d</i>., whereas a new chain +would cost 2<i>s</i>. 2<i>d</i>. But if we break up the piece of eight links, these +eight will join together the remaining eight pieces at a cost of 2<i>s</i>. +But there is a subtle way of even improving on this. Break up the two +pieces containing three and four links respectively, and these seven +will join together the remaining seven pieces at a cost of only 1<i>s</i>. +9<i>d</i>.</p> + +<hr style="width: 30%;" /> +<p><a name="X_422_THE_SABBATH_PUZZLEa" id="X_422_THE_SABBATH_PUZZLEa"></a><a href="#X_422_THE_SABBATH_PUZZLE"><b>422.—THE SABBATH PUZZLE.—<i>solution</i></b></a></p> + +<p>The way the author of the old poser proposed to solve the difficulty +was as follows: From the Jew's abode let the Christian and the Turk +set out on a tour round the globe, the Christian going due east and +the Turk due west. Readers of Edgar Allan Poe's story, <i>Three Sundays +in a Week</i>, or of Jules Verne's <i>Round the World in Eighty Days</i>, will +know that such a proceeding will result in the Christian's gaining a +day and in the Turk's losing a day, so that when they meet again at +the house of the Jew their reckoning will agree with his, and all +three may keep their Sabbath on the same day. The correctness of this +answer, of course, depends on the popular notion as to the definition +of a day—the average duration between successive sun-rises. It is an +old quibble, and quite sound enough for puzzle purposes. Strictly +speaking, the two travellers ought to change their reckonings on +passing the 180th meridian; otherwise we have to admit that at the +North or South Pole there would only be one Sabbath in seven years.</p> + +<hr style="width: 30%;" /> +<p><a name="X_423_THE_RUBY_BROOCHa" id="X_423_THE_RUBY_BROOCHa"></a><a href="#X_423_THE_RUBY_BROOCH"><b>423.—THE RUBY BROOCH.—<i>solution</i></b></a></p> + +<p>In this case we were shown a sketch of the brooch exactly as it +appeared after the four rubies had been stolen from it. The reader was +asked to show the positions from which the stones "may have been +taken;" for it is not possible to show precisely how the gems were +originally placed, because there are many such ways. But an important +point was the statement by Lady Littlewood's brother: "I know the +brooch well. It originally contained forty-five stones, and there are +now only forty-one. Somebody has stolen four rubies, and then reset as +small a number as possible in such a way that there shall always be +eight stones in any of the directions you have mentioned."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a423.png" width="400" height="410" alt="" title="" /> +</div> + +<p>The diagram shows the arrangement before the robbery. It will be seen +that it was only necessary to reset one ruby—the one in the centre. +Any solution involving the resetting of more than one stone is not in +accordance with the brother's statement, and must therefore be wrong. +The original arrangement was, of course, a little unsymmetrical, and +for this reason the brooch was described as "rather eccentric."</p> + +<hr style="width: 30%;" /> +<p><a name="X_424_THE_DOVETAILED_BLOCKa" id="X_424_THE_DOVETAILED_BLOCKa"></a><a href="#X_424_THE_DOVETAILED_BLOCK"><b>424.—THE DOVETAILED BLOCK.—<i>solution</i></b></a></p> + +<div class="figcenter" style="width: 300px;"> +<img src="images/a424.png" width="300" height="519" alt="" title="" /> +</div> + +<p>The mystery is made clear by the illustration. It will be seen at once +how the two pieces slide together in a diagonal direction.</p> + +<hr style="width: 30%;" /> +<p><a name="X_425_JACK_AND_THE_BEANSTALKa" id="X_425_JACK_AND_THE_BEANSTALKa"></a><a href="#X_425_JACK_AND_THE_BEANSTALK"><b>425.—JACK AND THE BEANSTALK.—<i>solution</i></b></a></p> + +<p>The serious blunder that the artist made in this drawing was in +depicting the tendrils of</p> + +<p><span class='pagenum'>Pg 250<a name="Page_250" id="Page_250"></a></span></p><div class="figcenter" style="width: 400px;"> +<img src="images/a425.png" width="400" height="402" alt="" title="" /> +</div> + +<p>the bean climbing spirally as at A above, whereas the French bean, or +scarlet runner, the variety clearly selected by the artist in the +absence of any authoritative information on the point, always climbs +as shown at B. Very few seem to be aware of this curious little fact. +Though the bean always insists on a sinistrorsal growth, as B, the hop +prefers to climb in a dextrorsal manner, as A. Why, is one of the +mysteries that Nature has not yet unfolded.</p> + +<hr style="width: 30%;" /> +<p><a name="X_426_THE_HYMN-BOARD_POSERa" id="X_426_THE_HYMN-BOARD_POSERa"></a><a href="#X_426_THE_HYMN-BOARD_POSER"><b>426.—THE HYMN-BOARD POSER.—<i>solution</i></b></a></p> + +<p>This puzzle is not nearly so easy as it looks at first sight. It was +required to find the smallest possible number of plates that would be +necessary to form a set for three hymn-boards, each of which would +show the five hymns sung at any particular service, and then to +discover the lowest possible cost for the same. The hymn-book contains +700 hymns, and therefore no higher number than 700 could possibly be +needed.</p> + +<p>Now, as we are required to use every legitimate and practical method +of economy, it should at once occur to us that the plates must be +painted on both sides; indeed, this is such a common practice in cases +of this kind that it would readily occur to most solvers. We should +also remember that some of the figures may possibly be reversed to +form other figures; but as we were given a sketch of the actual shapes +of these figures when painted on the plates, it would be seen that +though the 6's may be turned upside down to make 9's, none of the +other figures can be so treated.</p> + +<p>It will be found that in the case of the figures 1, 2, 3, 4, and 5, +thirty-three of each will be required in order to provide for every +possible emergency; in the case of 7, 8, and 0, we can only need +thirty of each; while in the case of the figure 6 (which may be +reversed for the figure 9) it is necessary to provide exactly +forty-two.</p> + +<p>It is therefore clear that the total number of figures necessary is +297; but as the figures are painted on both sides of the plates, only +149 such plates are required. At first it would appear as if one of +the plates need only have a number on one side, the other side being +left blank. But here we come to a rather subtle point in the problem.</p> + +<p>Readers may have remarked that in real life it is sometimes cheaper +when making a purchase to buy more articles than we require, on the +principle of a reduction on taking a quantity: we get more articles +and we pay less. Thus, if we want to buy ten apples, and the price +asked is a penny each if bought singly, or ninepence a dozen, we +should both save a penny and get two apples more than we wanted by +buying the full twelve. In the same way, since there is a regular +scale of reduction for plates painted alike, we actually save by +having two figures painted on that odd plate. Supposing, for example, +that we have thirty plates painted alike with 5 on one side and 6 on +the other. The rate would be 4¾<i>d</i>., and the cost 11<i>s</i>. 10½<i>d</i>. But +if the odd plate with, say, only a 5 on one side of it have a 6 +painted on the other side, we get thirty-one plates at the reduced +rate of 4½<i>d</i>., thus saving a farthing on each of the previous +thirty, and reducing the cost of the last one from 1<i>s</i>. to 4½<i>d</i>.</p> + +<p>But even after these points are all seen there comes in a new +difficulty: for although it will be found that all the 8's may be on +the backs of the 7's, we cannot have all the 2's on the backs of the +1's, nor all the 4 on the backs of the 3's, etc. There is a great +danger, in our attempts to get as many as possible painted alike, of +our so adjusting the figures that some particular combination of hymns +cannot be represented.</p> + +<p>Here is the solution of the difficulty that was sent to the vicar of +Chumpley St. Winifred. Where the sign is placed between two figures, +it implies that one of these figures is on one side of the plate and +the other on the other side.</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td></td><td></td><td></td><td align='center'><i>d</i>.</td><td></td><td align='center'>£</td><td align='center'><i>s</i>.</td><td align='right'><i>d</i>.</td></tr> +<tr><td align='right'>31</td><td align='center'>plates painted</td><td align='center'>5 X 9</td><td align='center'>@</td><td align='right'>4½</td><td align='center'>=</td><td align='right'>0</td><td align='right'>11</td><td align='right'>7½</td></tr> +<tr><td align='right'>30</td><td align='center'>"</td><td align='center'>7 X 8</td><td align='center'>@</td><td align='right'>4¾</td><td align='center'>=</td><td align='right'>0</td><td align='right'>11</td><td align='right'>10½</td></tr> +<tr><td align='right'>21</td><td align='center'>"</td><td align='center'>1 X 2</td><td align='center'>@</td><td align='right'>7</td><td align='center'>=</td><td align='right'>0</td><td align='right'>12</td><td align='right'>3</td></tr> +<tr><td align='right'>21</td><td align='center'>"</td><td align='center'>3 X 0</td><td align='center'>@</td><td align='right'>7</td><td align='center'>=</td><td align='right'>0</td><td align='right'>12</td><td align='right'>3</td></tr> +<tr><td align='right'>12</td><td align='center'>"</td><td align='center'>1 X 3</td><td align='center'>@</td><td align='right'>9¼</td><td align='center'>=</td><td align='right'>0</td><td align='right'>9</td><td align='right'>3</td></tr> +<tr><td align='right'>12</td><td align='center'>"</td><td align='center'>2 X 4</td><td align='center'>@</td><td align='right'>9¼</td><td align='center'>=</td><td align='right'>0</td><td align='right'>9</td><td align='right'>3</td></tr> +<tr><td align='right'>12</td><td align='center'>"</td><td align='center'>9 X 4</td><td align='center'>@</td><td align='right'>9¼</td><td align='center'>=</td><td align='right'>0</td><td align='right'>9</td><td align='right'>3</td></tr> +<tr><td align='right'>8</td><td align='center'>"</td><td align='center'>4 X 0</td><td align='center'>@</td><td align='right'>10¼</td><td align='right'>=</td><td align='center'>0</td><td align='right'>6</td><td align='right'>10</td></tr> +<tr><td align='right'>1</td><td align='center'>"</td><td align='center'>5 X 4</td><td align='center'>@</td><td align='right'>12</td><td align='right'>=</td><td align='center'>0</td><td align='right'>1</td><td align='right'>0</td></tr> +<tr><td align='right'>1</td><td align='center'>"</td><td align='center'>5 X 0</td><td align='center'>@</td><td align='right'>12</td><td align='right'>=</td><td align='center'>0</td><td align='right'>1</td><td align='right'>0</td></tr> +<tr><td align='right' class='bt'>149</td><td align='left' colspan='4'>plates @ 6<i>d</i>. each</td><td align='center'>=</td><td align='right'>3</td><td align='center'>14</td><td align='right'>6</td></tr> +<tr><td align='right'></td><td></td><td></td><td></td><td></td><td></td><td align='right' class='bt'>£7</td><td align='right' class='bt'>19</td><td align='right' class='bt'>1</td></tr> +</table></div> + + +<p>Of course, if we could increase the number of plates, we might get the +painting done for nothing, but such a contingency is prevented by the +condition that the fewest possible plates must be provided.</p> + +<p><span class='pagenum'>Pg 251<a name="Page_251" id="Page_251"></a></span>This puzzle appeared in <i>Tit-Bits</i>, and the following remarks, made +by me in the issue for 11th December 1897, may be of interest.</p> + +<p>The "Hymn-Board Poser" seems to have created extraordinary interest. +The immense number of attempts at its solution sent to me from all +parts of the United Kingdom and from several Continental countries +show a very kind disposition amongst our readers to help the worthy +vicar of Chumpley St. Winifred over his parochial difficulty. Every +conceivable estimate, from a few shillings up to as high a sum as +£1,347, 10<i>s</i>., seems to have come to hand. But the astonishing part of +it is that, after going carefully through the tremendous pile of +correspondence, I find that only one competitor has succeeded in +maintaining the reputation of the <i>Tit-Bits</i> solvers for their +capacity to solve anything, and his solution is substantially the same +as the one given above, the cost being identical. Some of his figures +are differently combined, but his grouping of the plates, as shown in +the first column, is exactly the same. Though a large majority of +competitors clearly hit upon all the essential points of the puzzle, +they completely collapsed in the actual arrangement of the figures. +According to their methods, some possible selection of hymns, such as +111, 112, 121, 122,211, cannot be set up. A few correspondents +suggested that it might be possible so to paint the 7's that upside +down they would appear as 2's or 4's; but this would, of course, be +barred out by the fact that a representation of the actual figures to +be used was given.</p> + +<hr style="width: 30%;" /> +<p><a name="X_427_PHEASANT-SHOOTINGa" id="X_427_PHEASANT-SHOOTINGa"></a><a href="#X_427_PHEASANT-SHOOTING"><b>427.—PHEASANT-SHOOTING.—<i>solution</i></b></a></p> + +<p>The arithmetic of this puzzle is very easy indeed. There were clearly +24 pheasants at the start. Of these 16 were shot dead, 1 was wounded +in the wing, and 7 got away. The reader may have concluded that the +answer is, therefore, that "seven remained." But as they flew away it +is clearly absurd to say that they "remained." Had they done so they +would certainly have been killed. Must we then conclude that the 17 +that were shot remained, because the others flew away? No; because the +question was not "how many remained?" but "how many still remained?" +Now the poor bird that was wounded in the wing, though unable to fly, +was very active in its painful struggles to run away. The answer is, +therefore, that the 16 birds that were shot dead "still remained," or +"remained still."</p> + +<hr style="width: 30%;" /> +<p><a name="X_428_THE_GARDENER_AND_THE_COOKa" id="X_428_THE_GARDENER_AND_THE_COOKa"></a><a href="#X_428_THE_GARDENER_AND_THE_COOK"><b>428.—THE GARDENER AND THE COOK.—<i>solution</i></b></a></p> + +<p>Nobody succeeded in solving the puzzle, so I had to let the cat out of +the bag—an operation that was dimly foreshadowed by the puss in the +original illustration. But I first reminded the reader that this +puzzle appeared on April 1, a day on which none of us ever resents +being made an "April Fool;" though, as I practically "gave the thing +away" by specially drawing attention to the fact that it was All +Fools' Day, it was quite remarkable that my correspondents, without a +single exception, fell into the trap.</p> + +<p>One large body of correspondents held that what the cook loses in +stride is exactly made up in greater speed; consequently both advance +at the same rate, and the result must be a tie. But another +considerable section saw that, though this might be so in a race 200 +ft. straight away, it could not really be, because they each go a +stated distance at "every bound," and as 100 is not an exact multiple +of 3, the gardener at his thirty-fourth bound will go 2 ft. beyond the +mark. The gardener will, therefore, run to a point 102 ft. straight +away and return (204 ft. in all), and so lose by 4 ft. This point +certainly comes into the puzzle. But the most important fact of all is +this, that it so happens that the gardener was a pupil from the +Horticultural College for Lady Gardeners at, if I remember aright, +Swanley; while the cook was a very accomplished French chef of the +hemale persuasion! Therefore "she (the gardener) made three bounds to +his (the cook's) two." It will now be found that while the gardener is +running her 204 ft. in 68 bounds of 3 ft., the somewhat infirm old +cook can only make 45<sup>1</sup>/<sub>3</sub> of his 2 ft. bounds, which equals 90 ft. 8 +in. The result is that the lady gardener wins the race by 109 ft. 4 +in. at a moment when the cook is in the air, one-third through his +46th bound.</p> + +<p>The moral of this puzzle is twofold: (1) Never take things for granted +in attempting to solve puzzles; (2) always remember All Fools' Day +when it comes round. I was not writing of <i>any</i> gardener and cook, but +of a <i>particular</i> couple, in "a race that I witnessed." The statement +of the eye-witness must therefore be accepted: as the reader was not +there, he cannot contradict it. Of course the information supplied was +insufficient, but the correct reply was: "Assuming the gardener to be +the 'he,' the cook wins by 4 ft.; but if the gardener is the 'she,' +then the gardener wins by 109 ft. 4 in." This would have won the +prize. Curiously enough, one solitary competitor got on to the right +track, but failed to follow it up. He said: "Is this a regular April 1 +catch, meaning that they only ran 6 ft. each, and consequently the +race was unfinished? If not, I think the following must be the +solution, supposing the gardener to be the 'he' and the cook the +'she.'" Though his solution was wrong even in the case he supposed, +yet he was the only person who suspected the question of sex.</p> + +<hr style="width: 30%;" /> +<p><a name="X_429_PLACING_HALFPENNIESa" id="X_429_PLACING_HALFPENNIESa"></a><a href="#X_429_PLACING_HALFPENNIES"><b>429.—PLACING HALFPENNIES.—<i>solution</i></b></a></p> + +<p>Thirteen coins may be placed as shown.</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/a429.png" width="400" height="248" alt="" title="" /> +</div> + +<hr style="width: 30%;" /> +<p><a name="X_430_FIND_THE_MANS_WIFEa" id="X_430_FIND_THE_MANS_WIFEa"></a><a href="#X_430_FIND_THE_MANS_WIFE"><b>430.—FIND THE MAN'S WIFE.—<i>solution</i></b></a></p> + +<p>There is no guessing required in this puzzle. It is all a question of +elimination. If we can pair off any five of the ladies with their +respective husbands, other than husband No. 10, then the remaining +lady must be No. 10's wife.</p> + +<p><span class='pagenum'>Pg 252<a name="Page_252" id="Page_252"></a></span></p> + +<p>I will show how this may be done. No. 8 is seen carrying a lady's +parasol in the same hand with his walking-stick. But every lady is +provided with a parasol, except No. 3; therefore No. 3 may be safely +said to be the wife of No. 8. Then No. 12 is holding a bicycle, and +the dress-guard and make disclose the fact that it is a lady's +bicycle. The only lady in a cycling skirt is No. 5; therefore we +conclude that No. 5 is No. 12's wife. Next, the man No. 6 has a dog, +and lady No. 11 is seen carrying a dog chain. So we may safely pair +No. 6 with No. 11. Then we see that man No. 2 is paying a newsboy for +a paper. But we do not pay for newspapers in this way before receiving +them, and the gentleman has apparently not taken one from the boy. But +lady No. 9 is seen reading a paper. The inference is obvious—that she +has sent the boy to her husband for a penny. We therefore pair No. 2 +with No. 9. We have now disposed of all the ladies except Nos. 1 and +7, and of all the men except Nos. 4 and 10. On looking at No. 4 we +find that he is carrying a coat over his arm, and that the buttons are +on the left side;—not on the right, as a man wears them. So it is a +lady's coat. But the coat clearly does not belong to No. 1, as she is +seen to be wearing a coat already, while No. 7 lady is very lightly +clad. We therefore pair No. 7 lady with man No. 4. Now the only lady +left is No. 1, and we are consequently forced to the conclusion that +she is the wife of No. 10. This is therefore the correct answer.</p> + + + +<hr style="width: 65%;" /><p><span class='pagenum'>Pg 253<a name="Page_253" id="Page_253"></a></span></p> +<h2><a name="INDEX" id="INDEX"></a><a href="#CONTENTS">INDEX.</a></h2> + + +<p> +<span style="margin-left: 2em;">Abbot's Puzzle, The, <a href="#Page_20">20</a>, <a href="#Page_161">161</a>.</span><br /> +<span style="margin-left: 3em;">—— Window, The, <a href="#Page_87">87</a>, <a href="#Page_213">213</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Academic Courtesies, <a href="#Page_18">18</a>, <a href="#Page_160">160</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Acrostic Puzzle, An, <a href="#Page_84">84</a>, <a href="#Page_210">210</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Adam and Eve and the Apples, <a href="#Page_18">18</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Aeroplanes, The Two, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Age and Kinship Puzzles, <a href="#Page_6">6</a>.</span><br /> +<span style="margin-left: 3em;">—— Concerning Tommy's, <a href="#Page_7">7</a>, <a href="#Page_153">153</a>.</span><br /> +<span style="margin-left: 3em;">—— Mamma's, <a href="#Page_7">7</a>, <a href="#Page_152">152</a>.</span><br /> +<span style="margin-left: 3em;">—— Mrs. Timpkins's, <a href="#Page_7">7</a>, <a href="#Page_152">152</a>.</span><br /> +<span style="margin-left: 3em;">—— Rover's, <a href="#Page_7">7</a>, <a href="#Page_152">152</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Ages, The Family, <a href="#Page_7">7</a>, <a href="#Page_152">152</a>.</span><br /> +<span style="margin-left: 3em;">—— Their, <a href="#Page_7">7</a>, <a href="#Page_152">152</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Alcuin, Abbot, <a href="#Page_20">20</a>, <a href="#Page_112">112</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Almonds, The Nine, <a href="#Page_64">64</a>, <a href="#Page_195">195</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Amazons, The, <a href="#Page_94">94</a>, <a href="#Page_221">221</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Andrews, W.S., <a href="#Page_125">125</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Apples, A Deal in, <a href="#Page_3">3</a>, <a href="#Page_149">149</a>.</span><br /> +<span style="margin-left: 3em;">—— Buying, <a href="#Page_6">6</a>, <a href="#Page_151">151</a>.</span><br /> +<span style="margin-left: 3em;">—— The Ten, <a href="#Page_64">64</a>, <a href="#Page_195">195</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Approximations in Dissection, <a href="#Page_28">28</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Arithmetical and Algebraical Problems, <a href="#Page_1">1</a>.</span><br /> +<span style="margin-left: 3em;">—— Various, <a href="#Page_17">17</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Arthur's Knights, King, <a href="#Page_77">77</a>, <a href="#Page_203">203</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Artillerymen's Dilemma, <a href="#Page_26">26</a>, <a href="#Page_167">167</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Asparagus, Bundles of, <a href="#Page_140">140</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Aspects all due South, <a href="#Page_137">137</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Associated Magic Squares, <a href="#Page_120">120</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Axiom, A Puzzling, <a href="#Page_138">138</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Bachet de Méziriac, <a href="#Page_90">90</a>, <a href="#Page_109">109</a>, <a href="#Page_112">112</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bachet's Square, <a href="#Page_90">90</a>, <a href="#Page_216">216</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Ball Problem, The, <a href="#Page_51">51</a>, <a href="#Page_183">183</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Ball, W.W. Rouse, <a href="#Page_109">109</a>, <a href="#Page_204">204</a>, <a href="#Page_248">248</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Balls, The Glass, <a href="#Page_78">78</a>, <a href="#Page_204">204</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Banker's Puzzle, The, <a href="#Page_25">25</a>, <a href="#Page_165">165</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bank Holiday Puzzle, A, <a href="#Page_73">73</a>, <a href="#Page_201">201</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Banner Puzzle, The, <a href="#Page_46">46</a>, <a href="#Page_179">179</a>.</span><br /> +<span style="margin-left: 3em;">—— St. George's, <a href="#Page_50">50</a>, <a href="#Page_182">182</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Barrel Puzzle, The, <a href="#Page_109">109</a>, <a href="#Page_235">235</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Barrels of Balsam, The, <a href="#Page_82">82</a>, <a href="#Page_208">208</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Beanfeast Puzzle, A, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Beef and Sausages, <a href="#Page_3">3</a>, <a href="#Page_149">149</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Beer, The Barrel of, <a href="#Page_13">13</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bell-ropes, Stealing the, <a href="#Page_49">49</a>, <a href="#Page_181">181</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bells, The Peal of, <a href="#Page_78">78</a>, <a href="#Page_204">204</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bergholt, E., <a href="#Page_116">116</a>, <a href="#Page_119">119</a>, <a href="#Page_125">125</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Betsy Ross Puzzle, The, <a href="#Page_40">40</a>, <a href="#Page_176">176</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bicycle Thief, The, <a href="#Page_6">6</a>, <a href="#Page_152">152</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bishops—Guarded, <a href="#Page_88">88</a>, <a href="#Page_214">214</a>.</span><br /> +<span style="margin-left: 3em;">—— in Convocation, <a href="#Page_89">89</a>, <a href="#Page_215">215</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, A New, <a href="#Page_98">98</a>, <a href="#Page_225">225</a>.</span><br /> +<span style="margin-left: 3em;">—— Unguarded, <a href="#Page_88">88</a>, <a href="#Page_214">214</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Board, The Chess-, <a href="#Page_85">85</a>.</span><br /> +<span style="margin-left: 3em;">—— in Compartments, The, <a href="#Page_102">102</a>, <a href="#Page_228">228</a>.</span><br /> +<span style="margin-left: 3em;">—— Setting the, <a href="#Page_105">105</a>, <a href="#Page_231">231</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Boards with Odd Number of Squares, <a href="#Page_86">86</a>, <a href="#Page_212">212</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Boat, Three Men in a, <a href="#Page_78">78</a>, <a href="#Page_204">204</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bookworm, The Industrious, <a href="#Page_143">143</a>, <a href="#Page_248">248</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Boothby, Guy, <a href="#Page_154">154</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Box, The Cardboard, <a href="#Page_49">49</a>, <a href="#Page_181">181</a>.</span><br /> +<span style="margin-left: 3em;">—— The Paper, <a href="#Page_40">40</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Boys and Girls, <a href="#Page_67">67</a>, <a href="#Page_197">197</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bridges, The Monk and the, <a href="#Page_75">75</a>, <a href="#Page_202">202</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Brigands, The Five, <a href="#Page_25">25</a>, <a href="#Page_164">164</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Brocade, The Squares of, <a href="#Page_47">47</a>, <a href="#Page_180">180</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Bun Puzzle, The, <a href="#Page_35">35</a>, <a href="#Page_170">170</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Busschop, Paul, <a href="#Page_172">172</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Buttons and String Method, <a href="#Page_230">230</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Cab Numbers, The, <a href="#Page_15">15</a>, <a href="#Page_157">157</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Calendar Puzzle, A, <a href="#Page_142">142</a>, <a href="#Page_247">247</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Canterbury Puzzles, The</i>, <a href="#Page_14">14</a>, <a href="#Page_28">28</a>, <a href="#Page_58">58</a>, <a href="#Page_117">117</a>, <a href="#Page_121">121</a>, <a href="#Page_195">195</a>, <a href="#Page_202">202</a>, <a href="#Page_205">205</a>, <a href="#Page_206">206</a>, <a href="#Page_212">212</a>, <a href="#Page_213">213</a>, <a href="#Page_217">217</a>, <a href="#Page_233">233</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Card Frame Puzzle, The, <a href="#Page_114">114</a>, <a href="#Page_238">238</a>.</span><br /> +<span style="margin-left: 3em;">—— Magic Squares, <a href="#Page_123">123</a>, <a href="#Page_244">244</a>.</span><br /> +<span style="margin-left: 3em;">—— Players, A Puzzle for, <a href="#Page_78">78</a>, <a href="#Page_203">203</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, The "T," <a href="#Page_115">115</a>, <a href="#Page_239">239</a>.</span><br /> +<span style="margin-left: 3em;">—— Triangles, <a href="#Page_115">115</a>, <a href="#Page_239">239</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cards, The Cross of, <a href="#Page_115">115</a>, <a href="#Page_238">238</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cardan, <a href="#Page_142">142</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Carroll, Lewis, <a href="#Page_43">43</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Castle Treasure, Stealing the, <a href="#Page_113">113</a>, <a href="#Page_237">237</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cats, the Wizard's, <a href="#Page_42">42</a>, <a href="#Page_178">178</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cattle, Judkins's, <a href="#Page_6">6</a>, <a href="#Page_151">151</a>.</span><br /> +<span style="margin-left: 3em;">—— Market, At a, <a href="#Page_1">1</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Census Puzzle, A, <a href="#Page_7">7</a>, <a href="#Page_152">152</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Century Puzzle, The, <a href="#Page_16">16</a>, <a href="#Page_158">158</a>.</span><br /> +<span style="margin-left: 3em;">—— The Digital, <a href="#Page_16">16</a>, <a href="#Page_159">159</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Chain Puzzle, A, <a href="#Page_144">144</a>, <a href="#Page_249">249</a>.</span><br /> +<span style="margin-left: 3em;">—— The Antiquary's, <a href="#Page_83">83</a>, <a href="#Page_209">209</a>.</span><br /> +<span style="margin-left: 3em;">—— The Cardboard, <a href="#Page_40">40</a>, <a href="#Page_176">176</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Change, Giving, <a href="#Page_4">4</a>, <a href="#Page_150">150</a>.</span><br /> +<span style="margin-left: 3em;">—— Ways of giving, <a href="#Page_151">151</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Changing Places, <a href="#Page_10">10</a>, <a href="#Page_154">154</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Channel Island, <a href="#Page_138">138</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Charitable Bequest, A, <a href="#Page_2">2</a>, 148</span><br /> +<br /> +<span style="margin-left: 2em;">Charity, Indiscriminate, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Checkmate, <a href="#Page_107">107</a>, <a href="#Page_233">233</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cheesemonger, The Eccentric, <a href="#Page_66">66</a>, <a href="#Page_196">196</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Chequered Board Divisions, <a href="#Page_85">85</a>, <a href="#Page_210">210</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cherries and Plums, <a href="#Page_56">56</a>, <a href="#Page_189">189</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Chess Puzzles, Dynamical, <a href="#Page_96">96</a>.</span><br /> +<span style="margin-left: 3em;">—— Statical, <a href="#Page_88">88</a>.</span><br /> +<span style="margin-left: 3em;">—— Various, <a href="#Page_105">105</a>.</span><br /><span class='pagenum'>Pg 254<a name="Page_254" id="Page_254"></a></span> +<span style="margin-left: 3em;">—— Queer, <a href="#Page_107">107</a>, <a href="#Page_233">233</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Chessboard, The, <a href="#Page_85">85</a>.</span><br /> +<span style="margin-left: 3em;">—— Fallacy, A, <a href="#Page_141">141</a>, <a href="#Page_247">247</a>.</span><br /> +<span style="margin-left: 3em;">—— Guarded, <a href="#Page_95">95</a>.</span><br /> +<span style="margin-left: 3em;">—— Non-attacking Arrangements, <a href="#Page_96">96</a>.</span><br /> +<span style="margin-left: 3em;">—— Problems, <a href="#Page_84">84</a>.</span><br /> +<span style="margin-left: 3em;">—— Sentence, The, <a href="#Page_87">87</a>, <a href="#Page_214">214</a>.</span><br /> +<span style="margin-left: 3em;">—— Solitaire, <a href="#Page_108">108</a>, <a href="#Page_234">234</a>.</span><br /> +<span style="margin-left: 3em;">—— The Chinese, <a href="#Page_87">87</a>, <a href="#Page_213">213</a>.</span><br /> +<span style="margin-left: 3em;">—— The Crowded, <a href="#Page_91">91</a>, <a href="#Page_217">217</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Chestnuts, Buying, <a href="#Page_6">6</a>, <a href="#Page_152">152</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Chinese Money, <a href="#Page_4">4</a>, <a href="#Page_150">150</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, Ancient, <a href="#Page_107">107</a>, <a href="#Page_233">233</a>.</span><br /> +<span style="margin-left: 3em;">—— —— <i>The Fashionable</i>, <a href="#Page_43">43</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Christmas Boxes, The, <a href="#Page_4">4</a>, <a href="#Page_150">150</a>.</span><br /> +<span style="margin-left: 3em;">—— Present, Mrs. Smiley's, <a href="#Page_46">46</a>, <a href="#Page_179">179</a>.</span><br /> +<span style="margin-left: 3em;">—— Pudding, The, <a href="#Page_43">43</a>, <a href="#Page_178">178</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cigar Puzzle, The, <a href="#Page_119">119</a>, <a href="#Page_242">242</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Circle, The Dissected, <a href="#Page_69">69</a>, <a href="#Page_197">197</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cisterns, How to Make, <a href="#Page_54">54</a>, <a href="#Page_188">188</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Civil Service "Howler," <a href="#Page_154">154</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Clare, John, <a href="#Page_58">58</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Clock Formulæ, <a href="#Page_154">154</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzles, <a href="#Page_9">9</a>.</span><br /> +<span style="margin-left: 3em;">—— The Club, <a href="#Page_10">10</a>, <a href="#Page_154">154</a>.</span><br /> +<span style="margin-left: 3em;">—— The Railway Station, <a href="#Page_11">11</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Clocks, The Three, <a href="#Page_11">11</a>, <a href="#Page_154">154</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Clothes Line Puzzle, The, <a href="#Page_50">50</a>, <a href="#Page_182">182</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Coast, Round the, <a href="#Page_63">63</a>, <a href="#Page_195">195</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Coincidence, A Queer, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Coins, The Broken, <a href="#Page_5">5</a>, <a href="#Page_150">150</a>.</span><br /> +<span style="margin-left: 3em;">—— The Ten, <a href="#Page_57">57</a>, <a href="#Page_190">190</a>.</span><br /> +<span style="margin-left: 3em;">—— Two Ancient, <a href="#Page_140">140</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Combination and Group Problems, <a href="#Page_76">76</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Compasses Puzzle, The, <a href="#Page_53">53</a>, <a href="#Page_186">186</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Composite Magic Squares, <a href="#Page_127">127</a>, <a href="#Page_246">246</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cone Puzzle, The, <a href="#Page_55">55</a>, <a href="#Page_188">188</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Corn, Reaping the, <a href="#Page_20">20</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cornfields, Farmer Lawrence's, <a href="#Page_101">101</a>, <a href="#Page_227">227</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Costermonger's Puzzle, The, <a href="#Page_6">6</a>, <a href="#Page_152">152</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Counter Problems, Moving, <a href="#Page_58">58</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, A New, <a href="#Page_98">98</a>, <a href="#Page_225">225</a>.</span><br /> +<span style="margin-left: 3em;">—— Solitaire, <a href="#Page_107">107</a>, <a href="#Page_234">234</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Counters, The Coloured, <a href="#Page_91">91</a>, <a href="#Page_217">217</a>.</span><br /> +<span style="margin-left: 3em;">—— The Forty-nine, <a href="#Page_92">92</a>, <a href="#Page_217">217</a>.</span><br /> +<span style="margin-left: 3em;">—— The Nine, <a href="#Page_14">14</a>, <a href="#Page_156">156</a>.</span><br /> +<span style="margin-left: 3em;">—— The Ten, <a href="#Page_15">15</a>, <a href="#Page_156">156</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Crescent Puzzle, The, <a href="#Page_52">52</a>, <a href="#Page_184">184</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Crescents of Byzantium, The Five, <a href="#Page_92">92</a>, <a href="#Page_219">219</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cricket Match, The Village, <a href="#Page_116">116</a>, <a href="#Page_239">239</a>.</span><br /> +<span style="margin-left: 3em;">—— Slow, <a href="#Page_116">116</a>, <a href="#Page_239">239</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cross and Triangle, <a href="#Page_35">35</a>, <a href="#Page_169">169</a>.</span><br /> +<span style="margin-left: 3em;">—— of Cards, <a href="#Page_115">115</a>, <a href="#Page_238">238</a>.</span><br /> +<span style="margin-left: 3em;">—— The Folded, <a href="#Page_35">35</a>, <a href="#Page_169">169</a>.</span><br /> +<span style="margin-left: 3em;">—— The Southern, <a href="#Page_93">93</a>, <a href="#Page_220">220</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Crosses, Counter, <a href="#Page_81">81</a>, <a href="#Page_207">207</a>.</span><br /> +<span style="margin-left: 3em;">—— from One, Two, <a href="#Page_35">35</a>, <a href="#Page_168">168</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Three, <a href="#Page_169">169</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Crossing River Problems, <a href="#Page_112">112</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Crusader, The, <a href="#Page_106">106</a>, <a href="#Page_232">232</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cubes, Sums of, <a href="#Page_165">165</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cushion Covers, The, <a href="#Page_46">46</a>, <a href="#Page_179">179</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cutting-out Puzzle, A, <a href="#Page_37">37</a>, <a href="#Page_172">172</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Cyclists' Feast, The, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Dairyman, The Honest, <a href="#Page_110">110</a>, <a href="#Page_235">235</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Definition, A Question of, <a href="#Page_23">23</a>, <a href="#Page_163">163</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">De Fonteney, <a href="#Page_112">112</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Deified Puzzle, The, <a href="#Page_74">74</a>, <a href="#Page_202">202</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Delannoy, <a href="#Page_112">112</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">De Morgan, A., <a href="#Page_27">27</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">De Tudor, Sir Edwyn, <a href="#Page_12">12</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Diabolique Magic Squares, <a href="#Page_120">120</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Diamond Puzzle, The, <a href="#Page_74">74</a>, <a href="#Page_202">202</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dice, A Trick with, <a href="#Page_116">116</a>, <a href="#Page_239">239</a>.</span><br /> +<span style="margin-left: 3em;">—— Game, The Montenegrin, <a href="#Page_119">119</a>, <a href="#Page_242">242</a>.</span><br /> +<span style="margin-left: 3em;">—— Numbers, The, <a href="#Page_17">17</a>, <a href="#Page_160">160</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Die, Painting the, <a href="#Page_84">84</a>, <a href="#Page_210">210</a>,</span><br /> +<br /> +<span style="margin-left: 2em;">Digital Analysis, <a href="#Page_157">157</a>, <a href="#Page_158">158</a>.</span><br /> +<span style="margin-left: 3em;">—— Division, <a href="#Page_16">16</a>, <a href="#Page_158">158</a>.</span><br /> +<span style="margin-left: 3em;">—— Multiplication, <a href="#Page_15">15</a>, <a href="#Page_156">156</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzles, <a href="#Page_13">13</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Digits, Adding the, <a href="#Page_16">16</a>, <a href="#Page_158">158</a>.</span><br /> +<span style="margin-left: 3em;">—— and Squares, <a href="#Page_14">14</a>, <a href="#Page_155">155</a>.</span><br /> +<span style="margin-left: 3em;">—— Odd and Even, <a href="#Page_14">14</a>, <a href="#Page_156">156</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dilemma, An Amazing, <a href="#Page_106">106</a>, <a href="#Page_233">233</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Diophantine Problem, <a href="#Page_164">164</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dissection Puzzle, An Easy, <a href="#Page_35">35</a>, <a href="#Page_170">170</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzles, <a href="#Page_27">27</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Various, <a href="#Page_35">35</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dividing Magic Squares, <a href="#Page_124">124</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Division, Digital, <a href="#Page_16">16</a>, <a href="#Page_158">158</a>.</span><br /> +<span style="margin-left: 3em;">—— Simple, <a href="#Page_23">23</a>, <a href="#Page_163">163</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Doctor's Query, The, <a href="#Page_109">109</a>, <a href="#Page_235">235</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dogs Puzzle, The Five, <a href="#Page_92">92</a>, <a href="#Page_218">218</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Domestic Economy, <a href="#Page_5">5</a>, <a href="#Page_151">151</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Domino Frame Puzzle, The, <a href="#Page_114">114</a>, <a href="#Page_238">238</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dominoes in Progression, <a href="#Page_114">114</a>, <a href="#Page_237">237</a>.</span><br /> +<span style="margin-left: 3em;">—— The Eighteen, <a href="#Page_123">123</a>, <a href="#Page_245">245</a>.</span><br /> +<span style="margin-left: 3em;">—— The Fifteen, <a href="#Page_83">83</a>, <a href="#Page_209">209</a>.</span><br /> +<span style="margin-left: 3em;">—— The Five, <a href="#Page_114">114</a>, <a href="#Page_238">238</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Donkey Riding, <a href="#Page_13">13</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dormitory Puzzle, A, <a href="#Page_81">81</a>, <a href="#Page_208">208</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dovetailed Block, The, <a href="#Page_145">145</a>, <a href="#Page_249">249</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Drayton's <i>Polyolbion</i>, <a href="#Page_58">58</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dungeon Puzzle, A, <a href="#Page_97">97</a>, <a href="#Page_224">224</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dungeons, The Siberian, <a href="#Page_123">123</a>, <a href="#Page_244">244</a>.</span><br /> +<span style="margin-left: 3em;">—— The Spanish, <a href="#Page_122">122</a>, <a href="#Page_244">244</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dutchmen's Wives, The, <a href="#Page_26">26</a>, <a href="#Page_167">167</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Dynamical Chess Puzzles, <a href="#Page_96">96</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Earth's Girdle, The, <a href="#Page_139">139</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Educational Times Reprints</i>, <a href="#Page_204">204</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Eggs, A Deal in, <a href="#Page_3">3</a>, <a href="#Page_149">149</a>.</span><br /> +<span style="margin-left: 3em;">—— Obtaining the, <a href="#Page_140">140</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Election, The Muddletown, <a href="#Page_19">19</a>, <a href="#Page_161">161</a>.</span><br /> +<span style="margin-left: 3em;">—— The Parish Council, <a href="#Page_19">19</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Eleven, The Mystic, <a href="#Page_16">16</a>, <a href="#Page_159">159</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Elopements, The Four, <a href="#Page_113">113</a>, <a href="#Page_237">237</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Elrick, E., <a href="#Page_231">231</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Engines, The Eight, <a href="#Page_61">61</a>, <a href="#Page_194">194</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Episcopal Visitation, An, <a href="#Page_98">98</a>, <a href="#Page_225">225</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Estate, Farmer Wurzel's, <a href="#Page_51">51</a>, <a href="#Page_184">184</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Estates, The Yorkshire, <a href="#Page_51">51</a>, <a href="#Page_183">183</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Euclid, <a href="#Page_31">31</a>, <a href="#Page_138">138</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Euler, L., <a href="#Page_165">165</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Exchange Puzzle, The, <a href="#Page_66">66</a>, <a href="#Page_196">196</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Fallacy, A Chessboard, <a href="#Page_141">141</a>, <a href="#Page_247">247</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Family Party, A, <a href="#Page_8">8</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Fare, The Passenger's, <a href="#Page_13">13</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Farmer and his Sheep, The, <a href="#Page_22">22</a>, <a href="#Page_163">163</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Fence Problem, A, <a href="#Page_21">21</a>, <a href="#Page_162">162</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Fences, The Landowner's, <a href="#Page_42">42</a>, <a href="#Page_178">178</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Fermat, <a href="#Page_164">164</a>, <a href="#Page_168">168</a>.</span><br /> +<br /><span class='pagenum'>Pg 255<a name="Page_255" id="Page_255"></a></span> +<span style="margin-left: 2em;">Find the Man's Wife, <a href="#Page_147">147</a>, <a href="#Page_251">251</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Fly on the Octahedron, The, <a href="#Page_70">70</a>, <a href="#Page_198">198</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Fog, Mr. Gubbins in a, <a href="#Page_18">18</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Football Players, The, <a href="#Page_116">116</a>, <a href="#Page_240">240</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Fraction, A Puzzling, <a href="#Page_138">138</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Fractions, More Mixed, <a href="#Page_16">16</a>, <a href="#Page_159">159</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Frame Puzzle, The Card, <a href="#Page_114">114</a>, <a href="#Page_238">238</a>.</span><br /> +<span style="margin-left: 3em;">—— —— The Domino, <a href="#Page_114">114</a>, <a href="#Page_238">238</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Frankenstein, E.N., <a href="#Page_232">232</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Frénicle, B., <a href="#Page_119">119</a>, <a href="#Page_168">168</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Frogs, The Educated, <a href="#Page_59">59</a>, 194-</span><br /> +<span style="margin-left: 3em;">—— The Four, <a href="#Page_103">103</a>, <a href="#Page_229">229</a>.</span><br /> +<span style="margin-left: 3em;">—— The Six, <a href="#Page_59">59</a>, <a href="#Page_193">193</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Frost, A.H., <a href="#Page_120">120</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Games, Puzzle, <a href="#Page_117">117</a>.</span><br /> +<span style="margin-left: 3em;">—— Problems concerning, <a href="#Page_114">114</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Garden, Lady Belinda's, <a href="#Page_52">52</a>, <a href="#Page_186">186</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, The, <a href="#Page_49">49</a>, <a href="#Page_182">182</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Gardener and the Cook, The, <a href="#Page_146">146</a>, <a href="#Page_251">251</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Geometrical Problems, <a href="#Page_27">27</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzles, Various, <a href="#Page_49">49</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">George and the Dragon, St., <a href="#Page_101">101</a>, <a href="#Page_227">227</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Getting Upstairs, Such a, <a href="#Page_143">143</a>, <a href="#Page_248">248</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Girdle, the Earth's, <a href="#Page_139">139</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Goat, The Tethered, <a href="#Page_53">53</a>, <a href="#Page_186">186</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Grand Lama's Problem, The, <a href="#Page_86">86</a>, <a href="#Page_212">212</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Grasshopper Puzzle, The, <a href="#Page_59">59</a>, <a href="#Page_193">193</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Greek Cross Puzzles, <a href="#Page_28">28</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Three from One, <a href="#Page_169">169</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Greyhound Puzzle, The, <a href="#Page_101">101</a>, <a href="#Page_227">227</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Grocer and Draper, The, <a href="#Page_5">5</a>, <a href="#Page_151">151</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Gros, L., <a href="#Page_248">248</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Group Problems, Combination and, <a href="#Page_76">76</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Groups, The Three, <a href="#Page_14">14</a>, <a href="#Page_156">156</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Guarini, <a href="#Page_229">229</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Hairdresser's Puzzle, The, <a href="#Page_137">137</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Halfpennies, Placing, <a href="#Page_147">147</a>, <a href="#Page_251">251</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hampton Court Maze solved, <a href="#Page_133">133</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hannah's Puzzle, <a href="#Page_75">75</a>, <a href="#Page_202">202</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hastings, The Battle of, <a href="#Page_23">23</a>, <a href="#Page_164">164</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hatfield Maze solved, <a href="#Page_136">136</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hat Puzzle, The, <a href="#Page_67">67</a>, <a href="#Page_196">196</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hat-peg Puzzle, The, <a href="#Page_93">93</a>, <a href="#Page_221">221</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hats, The Wrong, <a href="#Page_78">78</a>, <a href="#Page_203">203</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hay, The Trusses of, <a href="#Page_18">18</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Heads or Tails, <a href="#Page_22">22</a>, <a href="#Page_163">163</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hearthrug, Mrs. Hobson's, <a href="#Page_37">37</a>, <a href="#Page_172">172</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Helmholtz, Von, <a href="#Page_41">41</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Honey, The Barrels of, <a href="#Page_111">111</a>, <a href="#Page_236">236</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Honeycomb Puzzle, The, <a href="#Page_75">75</a>, <a href="#Page_202">202</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Horse Race Puzzle, The, <a href="#Page_117">117</a>, <a href="#Page_240">240</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Horseshoes, The Two, <a href="#Page_40">40</a>, <a href="#Page_175">175</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Houdin, <a href="#Page_68">68</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hydroplane Question, The, <a href="#Page_12">12</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Hymn-board Poser, The, <a href="#Page_145">145</a>, <a href="#Page_250">250</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Icosahedron Puzzle, The, <a href="#Page_70">70</a>, <a href="#Page_198">198</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Jack and the Beanstalk, <a href="#Page_145">145</a>, <a href="#Page_249">249</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Jackson, John, <a href="#Page_56">56</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Jaenisch, C.F. de, <a href="#Page_92">92</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Jampots, Arranging the, <a href="#Page_68">68</a>, <a href="#Page_197">197</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Jealous Husbands, Five, <a href="#Page_113">113</a>, <a href="#Page_236">236</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Joiner's Problem, The, <a href="#Page_36">36</a>, <a href="#Page_171">171</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Another, <a href="#Page_37">37</a>, <a href="#Page_171">171</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Jolly Gaol-Birds, Eight, <a href="#Page_122">122</a>, <a href="#Page_243">243</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Nine, <a href="#Page_122">122</a>, <a href="#Page_243">243</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Journey, The Queen's, <a href="#Page_100">100</a>, <a href="#Page_227">227</a>.</span><br /> +<span style="margin-left: 3em;">—— The Rook's, <a href="#Page_96">96</a>, <a href="#Page_224">224</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Junior Clerks' Puzzle, The, <a href="#Page_4">4</a>, <a href="#Page_150">150</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Juvenile Puzzle, A, <a href="#Page_68">68</a>, <a href="#Page_197">197</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Kangaroos, The Four, <a href="#Page_102">102</a>, <a href="#Page_228">228</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Kelvin, Lord, <a href="#Page_41">41</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Kennel Puzzle, The, <a href="#Page_105">105</a>, <a href="#Page_231">231</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">King and the Castles, The, <a href="#Page_56">56</a>, <a href="#Page_189">189</a>.</span><br /> +<span style="margin-left: 3em;">—— The Forsaken, <a href="#Page_106">106</a>, <a href="#Page_232">232</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Kite-flying Puzzle, A, <a href="#Page_54">54</a>, <a href="#Page_187">187</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Knight-guards, The, <a href="#Page_95">95</a>, <a href="#Page_222">222</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Knights, King Arthur's, <a href="#Page_77">77</a>, <a href="#Page_203">203</a>.</span><br /> +<span style="margin-left: 3em;">—— Tour, Magic, <a href="#Page_127">127</a>, <a href="#Page_247">247</a>.</span><br /> +<span style="margin-left: 3em;">—— —— The Cubic, <a href="#Page_103">103</a>, <a href="#Page_229">229</a>.</span><br /> +<span style="margin-left: 3em;">—— —— The Four, <a href="#Page_103">103</a>, <a href="#Page_229">229</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Labosne, A., <a href="#Page_25">25</a>, <a href="#Page_90">90</a>, <a href="#Page_216">216</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Labourer's Puzzle, The, <a href="#Page_18">18</a>, <a href="#Page_160">160</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Ladies' Diary</i>, <a href="#Page_26">26</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Lagrange, J.L., <a href="#Page_9">9</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Laisant, C.A., <a href="#Page_76">76</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Lamp-posts, Painting the, <a href="#Page_19">19</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Leap Year, <a href="#Page_155">155</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Ladies, The, <a href="#Page_19">19</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Legacy, A Puzzling, <a href="#Page_20">20</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Legal Difficulty, A, <a href="#Page_23">23</a>, <a href="#Page_163">163</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Le Plongeon, Dr., <a href="#Page_29">29</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Letter Block Puzzle, The, <a href="#Page_60">60</a>, <a href="#Page_194">194</a>.</span><br /> +<span style="margin-left: 3em;">—— Blocks, The Thirty-six, <a href="#Page_91">91</a>, <a href="#Page_216">216</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, The Fifteen, <a href="#Page_79">79</a>, <a href="#Page_205">205</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Level Puzzle, The, <a href="#Page_74">74</a>, <a href="#Page_202">202</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Linoleum Cutting, <a href="#Page_48">48</a>, <a href="#Page_181">181</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, Another, <a href="#Page_49">49</a>, <a href="#Page_181">181</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Lion and the Man, The, <a href="#Page_97">97</a>, <a href="#Page_224">224</a>.</span><br /> +<span style="margin-left: 3em;">—— Hunting, <a href="#Page_94">94</a>, <a href="#Page_222">222</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Lions and Crowns, <a href="#Page_85">85</a>, <a href="#Page_212">212</a>.</span><br /> +<span style="margin-left: 3em;">—— The Four, <a href="#Page_88">88</a>, <a href="#Page_214">214</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Lockers Puzzle, The, <a href="#Page_14">14</a>, <a href="#Page_156">156</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Locomotion and Speed Puzzles, <a href="#Page_11">11</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Lodging-house Difficulty, A, <a href="#Page_61">61</a>, <a href="#Page_194">194</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">London and Wise, <a href="#Page_131">131</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Loyd, Sam, <a href="#Page_8">8</a>, <a href="#Page_43">43</a>, <a href="#Page_44">44</a>, <a href="#Page_98">98</a>, <a href="#Page_144">144</a>, <a href="#Page_232">232</a>, <a href="#Page_233">233</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Lucas, Edouard, <a href="#Page_16">16</a>, <a href="#Page_76">76</a>, <a href="#Page_112">112</a>, <a href="#Page_121">121</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Luncheons, The City, <a href="#Page_77">77</a>, <a href="#Page_203">203</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">MacMahon, Major, <a href="#Page_109">109</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Magic Knight's Tour, <a href="#Page_127">127</a>, <a href="#Page_247">247</a>.</span><br /> +<span style="margin-left: 3em;">—— Square Problems, <a href="#Page_119">119</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Card, <a href="#Page_123">123</a>, <a href="#Page_244">244</a>.</span><br /> +<span style="margin-left: 3em;">—— —— of Composites, <a href="#Page_127">127</a>, <a href="#Page_246">246</a>.</span><br /> +<span style="margin-left: 3em;">—— —— of Primes, <a href="#Page_125">125</a>.</span><br /> +<span style="margin-left: 3em;">—— —— of Two Degrees, <a href="#Page_125">125</a>, <a href="#Page_245">245</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Two New, <a href="#Page_125">125</a>, <a href="#Page_245">245</a>.</span><br /> +<span style="margin-left: 3em;">—— Strips, <a href="#Page_121">121</a>, <a href="#Page_243">243</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Magics, Subtracting, Multiplying, and Dividing, <a href="#Page_124">124</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Maiden, The Languishing, <a href="#Page_97">97</a>, <a href="#Page_224">224</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mandarin's Puzzle, The, <a href="#Page_103">103</a>, <a href="#Page_230">230</a>.</span><br /> +<span style="margin-left: 3em;">—— "T" Puzzle, The, <a href="#Page_126">126</a>, <a href="#Page_246">246</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Marketing, Saturday, <a href="#Page_27">27</a>, <a href="#Page_168">168</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Market Women, The, <a href="#Page_3">3</a>, <a href="#Page_149">149</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mary and Marmaduke, <a href="#Page_7">7</a>, <a href="#Page_152">152</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mary, How Old was, <a href="#Page_8">8</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Massacre of Innocents, <a href="#Page_139">139</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Match Mystery, A, <a href="#Page_118">118</a>, <a href="#Page_241">241</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, A New, <a href="#Page_55">55</a>, <a href="#Page_188">188</a>.</span><br /> +<br /><span class='pagenum'>Pg 256<a name="Page_256" id="Page_256"></a></span> +<span style="margin-left: 2em;">Mates, Thirty-six, <a href="#Page_106">106</a>, <a href="#Page_233">233</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mazes and how to thread Them, <a href="#Page_127">127</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Measuring, Weighing, and Packing Puzzles, <a href="#Page_109">109</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, New, <a href="#Page_110">110</a>, <a href="#Page_235">235</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Meeting, The Suffragists', <a href="#Page_19">19</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mellor, W.M.F., <a href="#Page_242">242</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Ménages, Problême de, <a href="#Page_76">76</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mersenne, M., <a href="#Page_168">168</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mice, Catching the, <a href="#Page_65">65</a>, <a href="#Page_196">196</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Milkmaid Puzzle, The, <a href="#Page_50">50</a>, <a href="#Page_183">183</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Millionaire's Perplexity, The, <a href="#Page_3">3</a>, <a href="#Page_149">149</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mince Pies, The Twelve, <a href="#Page_57">57</a>, <a href="#Page_191">191</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mine, Inspecting a, <a href="#Page_71">71</a>, <a href="#Page_199">199</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Miners' Holiday, The, <a href="#Page_23">23</a>, <a href="#Page_163">163</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Miser, The Converted, <a href="#Page_21">21</a>, <a href="#Page_162">162</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mitre, Dissecting a, <a href="#Page_35">35</a>, <a href="#Page_170">170</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Monad, The Great, <a href="#Page_39">39</a>, <a href="#Page_174">174</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Money, A Queer Thing in, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>.</span><br /> +<span style="margin-left: 3em;">—— Boxes, The Puzzling, <a href="#Page_3">3</a>, <a href="#Page_149">149</a>.</span><br /> +<span style="margin-left: 3em;">——, Pocket, <a href="#Page_3">3</a>, <a href="#Page_149">149</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzles, <a href="#Page_1">1</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, A New, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>.</span><br /> +<span style="margin-left: 3em;">——, Square, <a href="#Page_3">3</a>, <a href="#Page_149">149</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Monist, The</i>, <a href="#Page_125">125</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Monk and the Bridges, The, <a href="#Page_75">75</a>, <a href="#Page_202">202</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Monstrosity, The, <a href="#Page_108">108</a>, <a href="#Page_234">234</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Montenegrin Dice Game, The, <a href="#Page_119">119</a>, <a href="#Page_242">242</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Moreau, <a href="#Page_76">76</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Morris, Nine Men's, <a href="#Page_58">58</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mosaics, A Problem in, <a href="#Page_90">90</a>, <a href="#Page_215">215</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mother and Daughter, <a href="#Page_7">7</a>, <a href="#Page_152">152</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Motor-car Race, The, <a href="#Page_117">117</a>, <a href="#Page_240">240</a>.</span><br /> +<span style="margin-left: 3em;">—— Tour, The, <a href="#Page_74">74</a>, <a href="#Page_201">201</a>.</span><br /> +<span style="margin-left: 3em;">—— Garage Puzzle, The, <a href="#Page_62">62</a>, <a href="#Page_195">195</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Motorists, A Puzzle for, <a href="#Page_73">73</a>, <a href="#Page_201">201</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Mouse-trap Puzzle, The, <a href="#Page_80">80</a>, <a href="#Page_206">206</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Moving Counter Problems, <a href="#Page_58">58</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Multiplication, Digital, <a href="#Page_15">15</a>, <a href="#Page_156">156</a>.</span><br /> +<span style="margin-left: 3em;">—— Queer, <a href="#Page_15">15</a>, <a href="#Page_157">157</a>.</span><br /> +<span style="margin-left: 3em;">—— Simple, <a href="#Page_23">23</a>, <a href="#Page_163">163</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Multiplying Magic Squares, <a href="#Page_124">124</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Muncey, J.N., <a href="#Page_125">125</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Murray, Sir James, <a href="#Page_44">44</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Napoleon, <a href="#Page_43">43</a>, <a href="#Page_44">44</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Nasik Magic Squares, <a href="#Page_120">120</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Neighbours, Next-Door, <a href="#Page_8">8</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Newton, Sir Isaac, <a href="#Page_56">56</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Nine Men's Morris, <a href="#Page_58">58</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Notation, Scales of, <a href="#Page_149">149</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Noughts and Crosses, <a href="#Page_58">58</a>, <a href="#Page_117">117</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Nouvelles Annales de Mathématiques</i>, <a href="#Page_14">14</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Number Checks Puzzle, The, <a href="#Page_16">16</a>, <a href="#Page_158">158</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Numbers, Curious, <a href="#Page_20">20</a>, <a href="#Page_162">162</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Nuts, The Bag of, <a href="#Page_8">8</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Observation, Defective, <a href="#Page_4">4</a>, <a href="#Page_150">150</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Octahedron, The Fly on the, <a href="#Page_70">70</a>, <a href="#Page_198">198</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Oval, How to draw an, <a href="#Page_50">50</a>, <a href="#Page_182">182</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Ovid's Game, <a href="#Page_58">58</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Packing in Russia, Gold, <a href="#Page_111">111</a>, <a href="#Page_236">236</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzles, Measuring, Weighing, and, <a href="#Page_109">109</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, A, <a href="#Page_111">111</a>, <a href="#Page_236">236</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pandiagonal Magic Squares, <a href="#Page_120">120</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Papa's Puzzle, <a href="#Page_53">53</a>, <a href="#Page_187">187</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pappus, <a href="#Page_53">53</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Paradox Party, The, <a href="#Page_137">137</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Party, A Family, <a href="#Page_8">8</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Patchwork Puzzles, <a href="#Page_46">46</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, Another, <a href="#Page_48">48</a>, <a href="#Page_180">180</a>.</span><br /> +<span style="margin-left: 3em;">—— The Silk, <a href="#Page_34">34</a>, <a href="#Page_168">168</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Patience, <i>Strand</i>, <a href="#Page_116">116</a>, <a href="#Page_239">239</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pawns, A Puzzle with, <a href="#Page_94">94</a>, <a href="#Page_222">222</a>.</span><br /> +<span style="margin-left: 3em;">—— Immovable, <a href="#Page_106">106</a>, <a href="#Page_233">233</a>.</span><br /> +<span style="margin-left: 3em;">—— The Six, <a href="#Page_107">107</a>, <a href="#Page_233">233</a>.</span><br /> +<span style="margin-left: 3em;">—— The Two, <a href="#Page_105">105</a>, <a href="#Page_231">231</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pearls, The Thirty-three, <a href="#Page_18">18</a>, <a href="#Page_160">160</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pebble Game, The, <a href="#Page_117">117</a>, <a href="#Page_240">240</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pedigree, A Mixed, <a href="#Page_8">8</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pellian Equation, <a href="#Page_164">164</a>, <a href="#Page_167">167</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pennies, The Five, <a href="#Page_143">143</a>, <a href="#Page_248">248</a>.</span><br /> +<span style="margin-left: 3em;">—— The Twelve, <a href="#Page_65">65</a>, <a href="#Page_195">195</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pension, Drawing her, <a href="#Page_12">12</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pentagon and Square, The, <a href="#Page_37">37</a>, <a href="#Page_172">172</a>.</span><br /> +<span style="margin-left: 3em;">—— Drawing a, <a href="#Page_37">37</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pfeffermann, M., <a href="#Page_125">125</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pheasant-Shooting, <a href="#Page_146">146</a>, <a href="#Page_251">251</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Philadelphia Maze solved, <a href="#Page_137">137</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pierrot's Puzzle, The, <a href="#Page_15">15</a>, <a href="#Page_156">156</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pigs, The Seven, <a href="#Page_41">41</a>, <a href="#Page_177">177</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Planck, C., <a href="#Page_220">220</a>, <a href="#Page_246">246</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Plane Paradox, <a href="#Page_138">138</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Plantation Puzzle, A, <a href="#Page_57">57</a>, <a href="#Page_189">189</a>.</span><br /> +<span style="margin-left: 3em;">—— The Burmese, <a href="#Page_58">58</a>, <a href="#Page_191">191</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Plates and Coins, <a href="#Page_65">65</a>, <a href="#Page_195">195</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Plums, The Baskets of, <a href="#Page_126">126</a>, <a href="#Page_245">245</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Poe, E.A., <a href="#Page_249">249</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Points and Lines Problems, <a href="#Page_56">56</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Postage Stamps, The Four, <a href="#Page_84">84</a>, <a href="#Page_210">210</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Post-Office Perplexity, A, <a href="#Page_1">1</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Potato Puzzle, The, <a href="#Page_41">41</a>, <a href="#Page_177">177</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Potatoes, The Basket of, <a href="#Page_13">13</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Precocious Baby, The, <a href="#Page_139">139</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Presents, Buying, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Prime Magic Squares, <a href="#Page_125">125</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Printer's Error, A, <a href="#Page_20">20</a>, <a href="#Page_162">162</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Prisoners, Exercise for, <a href="#Page_104">104</a>, <a href="#Page_230">230</a>.</span><br /> +<span style="margin-left: 3em;">—— The Ten, <a href="#Page_62">62</a>, <a href="#Page_195">195</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Probabilities, Two Questions in, <a href="#Page_5">5</a>, <a href="#Page_150">150</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Problems concerning Games, <a href="#Page_114">114</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Puss in the Corner, <a href="#Page_118">118</a>, <a href="#Page_240">240</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Puzzle Games, <a href="#Page_117">117</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pyramid, Painting a, <a href="#Page_83">83</a>, <a href="#Page_208">208</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pyramids, Square and Triangular, <a href="#Page_167">167</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Pythagoras, <a href="#Page_31">31</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">"Queen, The," <a href="#Page_120">120</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Queens and Bishop Puzzle, <a href="#Page_93">93</a>, <a href="#Page_219">219</a>.</span><br /> +<span style="margin-left: 3em;">—— The Eight, <a href="#Page_89">89</a>, <a href="#Page_215">215</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Queen's Journey, The, <a href="#Page_100">100</a>, <a href="#Page_227">227</a>.</span><br /> +<span style="margin-left: 3em;">—— Tour, The, <a href="#Page_98">98</a>, <a href="#Page_225">225</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Quilt, Mrs. Perkins's, <a href="#Page_47">47</a>, <a href="#Page_180">180</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Race Puzzle, The Horse-, <a href="#Page_117">117</a>, <a href="#Page_240">240</a>.</span><br /> +<span style="margin-left: 3em;">—— The Motor-car, <a href="#Page_117">117</a>, <a href="#Page_240">240</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Rackbrane's Little Loss, <a href="#Page_21">21</a>, <a href="#Page_163">163</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Railway Muddle, A, <a href="#Page_62">62</a>, <a href="#Page_194">194</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, A, <a href="#Page_61">61</a>, <a href="#Page_194">194</a>.</span><br /> +<span style="margin-left: 3em;">—— Stations, The Three, <a href="#Page_49">49</a>, <a href="#Page_182">182</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Rational Amusement for Winter Evenings</i>, <a href="#Page_56">56</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Rectangles, Counting the, <a href="#Page_105">105</a>, <a href="#Page_232">232</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Reiss, M., <a href="#Page_58">58</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Relationships, Queer, <a href="#Page_8">8</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Reversals, A Puzzle in, <a href="#Page_5">5</a>, <a href="#Page_151">151</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">River Axe, Crossing the, <a href="#Page_112">112</a>, <a href="#Page_236">236</a>.</span><br /> +<br /><span class='pagenum'>Pg 257<a name="Page_257" id="Page_257"></a></span> +<span style="margin-left: 2em;">River Problems, Crossing, <a href="#Page_112">112</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Rookery, The, <a href="#Page_105">105</a>, <a href="#Page_232">232</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Rook's Journey, The, <a href="#Page_96">96</a>, <a href="#Page_224">224</a>.</span><br /> +<span style="margin-left: 3em;">—— Tour, The, <a href="#Page_96">96</a>, <a href="#Page_223">223</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Rooks, The Eight, <a href="#Page_88">88</a>, <a href="#Page_214">214</a>.</span><br /> +<span style="margin-left: 3em;">—— The Two, <a href="#Page_117">117</a>, <a href="#Page_240">240</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Round Table, The, <a href="#Page_80">80</a>, <a href="#Page_205">205</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Route Problems, Unicursal and, <a href="#Page_68">68</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Ruby Brooch, The, <a href="#Page_144">144</a>, <a href="#Page_249">249</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Sabbath Puzzle, The, <a href="#Page_144">144</a>, <a href="#Page_249">249</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sailor's Puzzle, The, <a href="#Page_71">71</a>, <a href="#Page_199">199</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sayles, H.A., <a href="#Page_125">125</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Schoolboys, The Nine, <a href="#Page_80">80</a>, <a href="#Page_205">205</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Schoolgirls, The Fifteen, <a href="#Page_80">80</a>, <a href="#Page_204">204</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Scramble, The Great, <a href="#Page_19">19</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sculptor's Problem, The, <a href="#Page_23">23</a>, <a href="#Page_164">164</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Second Day of Week, <a href="#Page_139">139</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">See-Saw Puzzle, The, <a href="#Page_22">22</a>, <a href="#Page_163">163</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Semi-Nasik Magic Squares, <a href="#Page_120">120</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Senior and Junior, <a href="#Page_140">140</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sevens, The Four, <a href="#Page_17">17</a>, <a href="#Page_160">160</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sharp's Puzzle, <a href="#Page_230">230</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sheepfold, The, <a href="#Page_52">52</a>, <a href="#Page_184">184</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sheep Pens, The Six, <a href="#Page_55">55</a>, <a href="#Page_189">189</a>.</span><br /> +<span style="margin-left: 3em;">—— The Sixteen, <a href="#Page_80">80</a>, <a href="#Page_206">206</a>.</span><br /> +<span style="margin-left: 3em;">—— The Three, <a href="#Page_92">92</a>, <a href="#Page_217">217</a>.</span><br /> +<span style="margin-left: 3em;">—— Those Fifteen, <a href="#Page_77">77</a>, <a href="#Page_203">203</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Shopping Perplexity, A, <a href="#Page_4">4</a>, <a href="#Page_150">150</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Shuldham, C.D., <a href="#Page_125">125</a>, <a href="#Page_126">126</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Siberian Dungeons, The, <a href="#Page_123">123</a>, <a href="#Page_244">244</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Simpleton, The Village, <a href="#Page_11">11</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Skater, The Scientific, <a href="#Page_100">100</a>, <a href="#Page_226">226</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Skeat, Professor, <a href="#Page_127">127</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Solitaire, Central, <a href="#Page_63">63</a>, <a href="#Page_195">195</a>.</span><br /> +<span style="margin-left: 3em;">—— Chessboard, <a href="#Page_108">108</a>, <a href="#Page_234">234</a>.</span><br /> +<span style="margin-left: 3em;">—— Counter, <a href="#Page_107">107</a>, <a href="#Page_234">234</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sons, The Four, <a href="#Page_49">49</a>, <a href="#Page_181">181</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Spanish Dungeons, The, <a href="#Page_122">122</a>, <a href="#Page_244">244</a>.</span><br /> +<span style="margin-left: 3em;">—— Miser, The, <a href="#Page_24">24</a>, <a href="#Page_164">164</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Speed and Locomotion Puzzles, <a href="#Page_11">11</a>.</span><br /> +<span style="margin-left: 3em;">—— Average, <a href="#Page_11">11</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Spiral, Drawing a, <a href="#Page_50">50</a>, <a href="#Page_182">182</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Spot on the Table, The, <a href="#Page_17">17</a>, <a href="#Page_160">160</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Square Numbers, Check for, <a href="#Page_13">13</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Digital, <a href="#Page_16">16</a>, <a href="#Page_159">159</a>.</span><br /> +<span style="margin-left: 3em;">—— of Veneer, The, <a href="#Page_39">39</a>, <a href="#Page_175">175</a>.</span><br /> +<span style="margin-left: 3em;">—— Puzzle, An Easy, <a href="#Page_35">35</a>, <a href="#Page_170">170</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Squares, A Problem in, <a href="#Page_23">23</a>, <a href="#Page_163">163</a>.</span><br /> +<span style="margin-left: 3em;">—— Circling the, <a href="#Page_21">21</a>, <a href="#Page_162">162</a>.</span><br /> +<span style="margin-left: 3em;">—— Difference of Two, <a href="#Page_167">167</a>.</span><br /> +<span style="margin-left: 3em;">—— Magic, <a href="#Page_119">119</a>.</span><br /> +<span style="margin-left: 3em;">—— Sum of Two, <a href="#Page_165">165</a>, <a href="#Page_175">175</a>.</span><br /> +<span style="margin-left: 3em;">—— The Chocolate, <a href="#Page_35">35</a>, <a href="#Page_170">170</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Stalemate, <a href="#Page_106">106</a>, <a href="#Page_232">232</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Stamp-licking, The Gentle Art of, <a href="#Page_91">91</a>, <a href="#Page_217">217</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Star Puzzle, The, <a href="#Page_99">99</a>, <a href="#Page_226">226</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Stars, The Eight, <a href="#Page_89">89</a>, <a href="#Page_215">215</a>.</span><br /> +<span style="margin-left: 3em;">—— The Forty-nine, <a href="#Page_100">100</a>, <a href="#Page_226">226</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Statical Chess Puzzles, <a href="#Page_88">88</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sticks, The Eight, <a href="#Page_53">53</a>, <a href="#Page_186">186</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Stonemason's Problem, The, <a href="#Page_25">25</a>, <a href="#Page_165">165</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Stop-watch, The, <a href="#Page_11">11</a>, <a href="#Page_154">154</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Strand Magazine, The</i>, <a href="#Page_44">44</a>, <a href="#Page_116">116</a>, <a href="#Page_220">220</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Strand</i> Patience, <a href="#Page_116">116</a>, <a href="#Page_239">239</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Stream, Crossing the, <a href="#Page_112">112</a>, <a href="#Page_236">236</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Strutt, Joseph, <a href="#Page_59">59</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Subtracting Magic Squares, <a href="#Page_124">124</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Sultan's Army, The, <a href="#Page_25">25</a>, <a href="#Page_165">165</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Suppers, The New Year's Eve, <a href="#Page_3">3</a>, <a href="#Page_149">149</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Surname, Find Ada's, <a href="#Page_27">27</a>, <a href="#Page_168">168</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Swastika, The, <a href="#Page_29">29</a>, <a href="#Page_31">31</a>, <a href="#Page_169">169</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">"T" Card Puzzle, The, <a href="#Page_115">115</a>, <a href="#Page_239">239</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Table, The Round, <a href="#Page_80">80</a>, <a href="#Page_205">205</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Table-top and Stools, The, <a href="#Page_38">38</a>, <a href="#Page_173">173</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Tangram Paradox, A, <a href="#Page_43">43</a>, <a href="#Page_178">178</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Target, The Cross, <a href="#Page_84">84</a>, <a href="#Page_210">210</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Tarry, <a href="#Page_112">112</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Tartaglia, <a href="#Page_25">25</a>, <a href="#Page_109">109</a>, <a href="#Page_112">112</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Tea, Mixing the, <a href="#Page_111">111</a>, <a href="#Page_235">235</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Telegraph Posts, The, <a href="#Page_139">139</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Tennis Tournament, A, <a href="#Page_78">78</a>, <a href="#Page_203">203</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Tetrahedron, Building the, <a href="#Page_82">82</a>, <a href="#Page_208">208</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Thief, Catching the, <a href="#Page_19">19</a>, <a href="#Page_161">161</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Thrift, A Study in, <a href="#Page_25">25</a>, <a href="#Page_166">166</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Thompson, W.H., <a href="#Page_232">232</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Ticket Puzzle, The Excursion, <a href="#Page_5">5</a>, <a href="#Page_151">151</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Time Puzzle, A, <a href="#Page_10">10</a>, <a href="#Page_153">153</a>.</span><br /> +<span style="margin-left: 3em;">—— What was the, <a href="#Page_10">10</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Tiring Irons, The, <a href="#Page_142">142</a>, <a href="#Page_247">247</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Tit-Bits</i>, <a href="#Page_58">58</a>, <a href="#Page_79">79</a>, <a href="#Page_124">124</a>, <a href="#Page_251">251</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Torn Number, The, <a href="#Page_20">20</a>, <a href="#Page_162">162</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Torpedo Practice, <a href="#Page_67">67</a>, <a href="#Page_196">196</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Tour, The Cyclists', <a href="#Page_71">71</a>, <a href="#Page_199">199</a>.</span><br /> +<span style="margin-left: 3em;">—— The Grand, <a href="#Page_72">72</a>, <a href="#Page_200">200</a>.</span><br /> +<span style="margin-left: 3em;">—— The Queen's, <a href="#Page_98">98</a>, <a href="#Page_225">225</a>.</span><br /> +<span style="margin-left: 3em;">—— The Rook's, <a href="#Page_96">96</a>, <a href="#Page_223">223</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Towns, Visiting the, <a href="#Page_70">70</a>, <a href="#Page_198">198</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Trains, The Two, <a href="#Page_11">11</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Treasure Boxes, The Nine, <a href="#Page_24">24</a>, <a href="#Page_164">164</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Trees, The Twenty-one, <a href="#Page_57">57</a>, <a href="#Page_190">190</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Trémaux, M., <a href="#Page_133">133</a>, <a href="#Page_135">135</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Triangle, The Dissected, <a href="#Page_38">38</a>, <a href="#Page_173">173</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Triangular Numbers, <a href="#Page_13">13</a>, <a href="#Page_25">25</a>, <a href="#Page_166">166</a>.</span><br /> +<span style="margin-left: 3em;">—— —— Check for, <a href="#Page_13">13</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Troublesome Eight, The, <a href="#Page_121">121</a>, <a href="#Page_242">242</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Tube Inspector's Puzzle, The, <a href="#Page_69">69</a>, <a href="#Page_198">198</a>.</span><br /> +<span style="margin-left: 3em;">—— Railway, Heard on the, <a href="#Page_8">8</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Turks and Russians, <a href="#Page_58">58</a>, <a href="#Page_191">191</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Turnings, The Fifteen, <a href="#Page_70">70</a>, <a href="#Page_198">198</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Twickenham Puzzle, The, <a href="#Page_60">60</a>, <a href="#Page_194">194</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Two Pieces Problem, The, <a href="#Page_96">96</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Unclassified Puzzles, <a href="#Page_142">142</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Unicursal and Route Problems, <a href="#Page_68">68</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Union Jack, The, <a href="#Page_50">50</a>, <a href="#Page_69">69</a>, <a href="#Page_197">197</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Vandermonde, A., <a href="#Page_58">58</a>, <a href="#Page_103">103</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Veil, Under the, <a href="#Page_90">90</a>, <a href="#Page_216">216</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Verne, Jules, <a href="#Page_249">249</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Victoria Cross Puzzle, The, <a href="#Page_60">60</a>, <a href="#Page_194">194</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Village, A Wonderful, <a href="#Page_142">142</a>, <a href="#Page_247">247</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Villages, The Three, <a href="#Page_12">12</a>, <a href="#Page_155">155</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Villas, The Eight, <a href="#Page_80">80</a>, <a href="#Page_206">206</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Vortex Rings, <a href="#Page_40">40</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Voter's Puzzle, The, <a href="#Page_75">75</a>, <a href="#Page_202">202</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Wall, The Puzzle, <a href="#Page_52">52</a>, <a href="#Page_184">184</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wallis, J., <a href="#Page_142">142</a>.</span><br /> +<span style="margin-left: 3em;">—— (Another), <a href="#Page_220">220</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Walls, The Garden, <a href="#Page_52">52</a>, <a href="#Page_185">185</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wapshaw's Wharf Mystery, The, <a href="#Page_10">10</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">War Puzzle Game, The, <a href="#Page_118">118</a>, <a href="#Page_240">240</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wassail Bowl, The, <a href="#Page_109">109</a>, <a href="#Page_235">235</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Watch, A Puzzling, <a href="#Page_10">10</a>, <a href="#Page_153">153</a>.</span><br /> +<br /><span class='pagenum'>Pg 258<a name="Page_258" id="Page_258"></a></span> +<span style="margin-left: 2em;">Water, Gas, and Electricity, <a href="#Page_73">73</a>, <a href="#Page_200">200</a>.</span><br /> +<br /> +<span style="margin-left: 2em;"><i>Weekly Dispatch, The</i>, <a href="#Page_28">28</a>, <a href="#Page_124">124</a>, <a href="#Page_125">125</a>, <a href="#Page_146">146</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Weighing Puzzles, Measuring, Packing, and, <a href="#Page_109">109</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wheels, Concerning, <a href="#Page_55">55</a>, <a href="#Page_188">188</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Who was First? <a href="#Page_142">142</a>, <a href="#Page_247">247</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Whyte, W.T., <a href="#Page_147">147</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Widow's Legacy, The, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wife, Find the Man's, <a href="#Page_147">147</a>, <a href="#Page_251">251</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wilkinson, Rev. Mr., <a href="#Page_193">193</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wilson, Professor, <a href="#Page_29">29</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wilson's Poser, <a href="#Page_9">9</a>, <a href="#Page_153">153</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wine and Water, <a href="#Page_110">110</a>, <a href="#Page_235">235</a>.</span><br /> +<span style="margin-left: 3em;">—— The Keg of, <a href="#Page_110">110</a>, <a href="#Page_235">235</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Wotherspoon, G., <a href="#Page_244">244</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Yacht race, The, <a href="#Page_99">99</a>, <a href="#Page_226">226</a>.</span><br /> +<br /> +<span style="margin-left: 2em;">Youthful Precocity, <a href="#Page_1">1</a>, <a href="#Page_148">148</a>.</span><br /> +<br /> +<br /> +<span style="margin-left: 2em;">Zeno, <a href="#Page_139">139</a>.</span><br /> +</p> + +<hr style="width: 65%;" /><p><span class='pagenum'>Pg 259<a name="Page_259" id="Page_259"></a></span></p> +<h2>THE END.</h2> + + + + + + + + +<pre> + + + + + +End of Project Gutenberg's Amusements in Mathematics, by Henry Ernest Dudeney + +*** END OF THIS PROJECT GUTENBERG EBOOK AMUSEMENTS IN MATHEMATICS *** + +***** This file should be named 16713-h.htm or 16713-h.zip ***** +This and all associated files of various formats will be found in: + https://www.gutenberg.org/1/6/7/1/16713/ + +Produced by Stephen Schulze, Jonathan Ingram and the Online +Distributed Proofreading Team at https://www.pgdp.net + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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