Martin Gardner was a renowned author who published over 70 books on subjects from science and math to poetry and religion. He also had a lifelong passion for magic tricks and puzzles. Well known for his mathematical games column in Scientific American and his "Trick of the Month" in Physics Teacher magazine, Gardner attracted a loyal following with his intelligence, wit, and imagination.

Martin Gardner: A Remembrance
The worldwide mathematical community was saddened by the death of Martin Gardner on May 22, 2010. Martin was 95 years old when he died, and had written 70 or 80 books during his long lifetime as an author. Martin's first Dover books were published in 1956 and 1957: Mathematics, Magic and Mystery, one of the first popular books on the intellectual excitement of mathematics to reach a wide audience, and Fads and Fallacies in the Name of Science, certainly one of the first popular books to cast a devastatingly skeptical eye on the claims of pseudoscience and the many guises in which the modern world has given rise to it. Both of these pioneering books are still in print with Dover today along with more than a dozen other titles of Martin's books. They run the gamut from his elementary Codes, Ciphers and Secret Writing, which has been enjoyed by generations of younger readers since the 1980s, to the more demanding The New Ambidextrous Universe: Symmetry and Asymmetry from Mirror Reflections to Superstrings, which Dover published in its final revised form in 2005.

To those of us who have been associated with Dover for a long time, however, Martin was more than an author, albeit a remarkably popular and successful one. As a member of the small group of long-time advisors and consultants, which included NYU's Morris Kline in mathematics, Harvard's I. Bernard Cohen in the history of science, and MIT's J. P. Den Hartog in engineering, Martin's advice and editorial suggestions in the formative 1950s helped to define the Dover publishing program and give it the point of view which — despite many changes, new directions, and the consequences of evolution — continues to be operative today.

In the Author's Own Words:
"Politicians, real-estate agents, used-car salesmen, and advertising copy-writers are expected to stretch facts in self-serving directions, but scientists who falsify their results are regarded by their peers as committing an inexcusable crime. Yet the sad fact is that the history of science swarms with cases of outright fakery and instances of scientists who unconsciously distorted their work by seeing it through lenses of passionately held beliefs."

"A surprising proportion of mathematicians are accomplished musicians. Is it because music and mathematics share patterns that are beautiful?" — Martin Gardner

My Best Mathematical and Logic Puzzles

By Martin Gardner

Dover Publications, Inc.

Copyright © 1994 Martin Gardner
All rights reserved.
ISBN: 978-0-486-28152-0

Contents

PUZZLES,
1. The Returning Explorer,
2. Draw Poker,
3. The Mutilated Chessboard,
4. The Fork in the Road,
5. Scrambled Box Tops,
6. Cutting the Cube,
7. Bronx vs. Brooklyn,
8. The Early Commuter,
9. The Counterfeit Coins,
10. The Touching Cigarettes,
11. Two Ferryboats,
12. Guess the Diagonal,
13. Cross the Network,
14. The 12 Matches,
15. Hole in the Sphere,
16. The Amorous Bugs,
17. How Many Children?,
18. The Twiddled Bolts,
19. The Flight around the World,
20. The Repetitious Number,
21. The Colliding Missiles,
22. The Sliding Pennies,
23. Handshakes and Networks,
24. The Triangular Duel,
25. Crossing the Desert,
26. Lord Dunsany's Chess Problem,
27. The Lonesome 8,
28. Dividing the Cake,
29. The Folded Sheet,
30. Water and Wine,
31. The Absent-Minded Teller,
32. Acute Dissection,
33. How Long Is a "Lunar"?,
34. The Game of Googol,
35. Marching Cadets and a Trotting Dog,
36. White, Black and Brown,
37. The Plane in the Wind,
38. What Price Pets?,
39. The Game of Hip,
40. A Switching Puzzle,
41. Beer Signs on the Highway,
42. The Sliced Cube and the Sliced Doughnut,
43. Bisecting Yin and Yang,
44. The Blue-Eyed Sisters,
45. How Old Is the Rose-Red City?,
46. Tricky Track,
47. Termite and 27 Cubes,
48. Collating the Coins,
49. Time the Toast,
50. A Fixed-Point Theorem,
51. How Did Kant Set His Clock?,
52. Playing Twenty Questions when Probability Values Are Known,
53. Don't Mate in One,
54. Find the Hexahedrons,
55. Out with the Onion,
56. Cut Down the Cuts,
57. Dissection Dilemma,
58. Interrupted Bridge,
59. Dash It All!,
60. Move the Queen,
61. Read the Hieroglyphics,
62. Crazy Cut,
63. Find the Oddball,
64. Big Cross-Out Swindle,
65. Reverse the Dog,
66. Funny Fold,
ANSWERS,

CHAPTER 1

PUZZLES

1. The Returning Explorer

An old riddle runs as follows. An explorer walks one mile due south, turns and walks one mile due east, turns again and walks one mile due north. He finds himself back where he started. He shoots a bear. What color is the bear? The time-honored answer is: "White," because the explorer must have started at the North Pole. But not long ago someone made the discovery that the North Pole is not the only starting point that satisfies the given conditions! Can you think of any other spot on the globe from which one could walk a mile south, a mile east, a mile north and find himself back at his original location?

2. Draw Poker

Two men play a game of draw poker in the following curious manner. They spread a deck of 52 cards face up on the table so that they can see all the cards. The first player draws a hand by picking any five cards he chooses. The second player does the same. The first player now may keep his original hand or draw up to five cards. His discards are put aside out of the game. The second player may now draw likewise. The person with the higher hand then wins. Suits have equal value, so that two flushes tie unless one is made of higher cards. After a while the players discover that the first player can always win if he draws his first hand correctly. What hand must this be?

3. The Mutilated Chessboard

The props for this problem are a chessboard and 32 dominoes. Each domino is of such size that it exactly covers two adjacent squares on the board. The 32 dominoes therefore can cover all 64 of the chessboard squares. But now suppose we cut off two squares at diagonally opposite corners of the board and discard one of the dominoes. Is it possible to place the 31 dominoes on the board so that all the remaining 62 squares are covered? If so, show how it can be done. If not, prove it impossible.

4. The Fork in the Road

Here's a recent twist on an old type of logic puzzle. A logician vacationing in the South Seas finds himself on an island inhabited by the two proverbial tribes of liars and truth-tellers. Members of one tribe always tell the truth, members of the other always lie. He comes to a fork in a road and has to ask a native bystander which branch he should take to reach a village. He has no way of telling whether the native is a truth-teller or a liar. The logician thinks a moment, then asks one question only. From the reply he knows which road to take. What question does he ask?

5. Scrambled Box Tops

Imagine that you have three boxes, one containing two black marbles, one containing two white marbles, and the third, one black marble and one white marble. The boxes were labeled for their contents—BB, WW and BW—but someone has switched the labels so that every box is now incorrectly labeled. You are allowed to take one marble at a time out of any box, without looking inside, and by this process of sampling you are to determine the contents of all three boxes. What is the smallest number of drawings needed to do this?

6. Cutting the Cube

A carpenter, working with a buzz saw, wishes to cut a wooden cube, three inches on a side, into 27 one-inch cubes. He can do this easily by making six cuts through the cube, keeping the pieces together in the cube shape. Can he reduce the number of necessary cuts by rearranging the pieces after each cut?

7. Bronx vs. Brooklyn

A young man lives in Manhattan near a subway express station. He has two girl friends, one in Brooklyn, one in The Bronx. To visit the girl in Brooklyn he takes a train on the downtown side of the platform; to visit the girl in The Bronx he takes a train on the uptown side of the same platform. Since he likes both girls equally well, he simply takes the first train that comes along. In this way he lets chance determine whether he rides to The Bronx or to Brooklyn. The young man reaches the subway platform at a random moment each Saturday afternoon. Brooklyn and Bronx trains arrive at the station equally often—every 10 minutes. Yet for some obscure reason he finds himself spending most of his time with the girl in Brooklyn: in fact on the average he goes there nine times out of ten. Can you think of a good reason why the odds so heavily favor Brooklyn?

8. The Early Commuter

A commuter is in the habit of arriving at his suburban station each evening exactly at five o'clock. His wife always meets the train and drives him home. One day he takes an earlier train, arriving at the station at four. The weather is pleasant, so instead of telephoning home he starts walking along the route always taken by his wife. They meet somewhere on the way. He gets into the car and they drive home, arriving at their house ten minutes earlier than usual. Assuming that the wife always drives at a constant speed, and that on this occasion she left just in time to meet the five o'clock train, can you determine how long the husband walked before he was picked up?

9. The Counterfeit Coins

In recent years a number of clever coin-weighing or ball-weighing problems have aroused widespread interest. Here is a new and charmingly simple variation. You have 10 stacks of coins, each consisting of 10 half-dollars. One entire stack is...