Prove that you can not cover the plane with infinite strips which have a total sum of their widths equal to 1.
SOLUTION
Take a circle with radius 1 in the plane. A strip with width X covers at most an area of 2X of the circle. Therefore all strips cover at most an area of 2, which is smaller than the total area of the circle (~3.14).
52 cards – 2 of clubs to Ace of clubs, 2 of diamonds to Ace of diamonds, 2 of hearts to Ace of hearts, and 2 of spades to Ace of spades – are arranged in a deck. We shuffle them in the following manner:
We take the top card and put in a random place inside the deck.
Once we get to the King of spades and put it somewhere in the deck, we stop.
Show that this method shuffles the deck uniformly, i.e. every permutation has the same chance to appear.
SOLUTION
Notice that at all times the cards below the King of spades are shuffled uniformly. Therefore at the end, after we put the King of spades in a random place inside the deck, the entire shuffle will be uniform as well.
The chances are you have already seen the hundreds of optical illusions we have collected for you on Puzzle Prime, but have you ever encountered any audio illusions? The YouTube channel AsapSCIENCE has created a short video in which they present and explain some of the most famous audio illusions, such as the McGurk effect and the Tritone paradox. Watch their video below and see if you can trust your ears.
Can you construct a convex polyhedron, such that no two of its faces have the same number of edges?
SOLUTION
No, you can not construct such a polyhedron. Assume the opposite and consider its face, which has the largest number of sides, say k. Then the polyhedron contains at least k more faces with different numbers of sides, all less than m. However, this is clearly impossible.
Someone stole gold coins from a museum near the park. No one saw the thief take the coins, so there isn’t a description of the robber. Slylock Fox suspects one of the creatures in the park is the thief. Which one?
SOLUTION
The raccoon on the seesaw couldn’t hold the heavier bear off the ground unless he was carrying something heavy. Since gold is one of the heaviest metals, Slylock suspects the raccoon is the thief and has hidden the coins in his clothes.
In 1996, just a day before the election of the 40th President of US, the New York Times published a curious crossword. In the 8th row, the solver should discover a phrase – the “lead story of tomorrow’s newspaper”. More precisely – the name of the future President of the country appears there. But how could New York Times know whether it was going to be Clinton or Bob Dole?
ACROSS:
1. “___ your name” (Mamas and Papas lyric) 6. Fell behind slightly 15. Euripides tragedy 16. Free 17. Forecast 19. Be bedridden 20. Journalist Stewart 21. Rosetta ??? 22. 1960s espionage series 24. ___ Perigion 25. Qulting party 26. “Drying out” program 28. Umpire’s call 30. Tease 34. Tease 36. Standard 38. “The Tell-Tale Heart” writer 39. Lead story in tomorrow’s newspaper, with 43A 43. See 39A 45. Gold: Prefix 46. ___ Lee cakes 48. Bobble the ball 49. Spanish aunts 51. Obi 53. Bravery 57. Small island 59. Daddies 61. Theda of 1917’s “Cleopatra” 62. Employee motivator 65. Otherworldly 67. Treasure hunter’s aid 68. Title for 39A next year 71. Exclusion from social events 72. Fab Four name 73. They may get tied up in knots 74. Begin, as a maze
DOWN:
1. Disable 2. Cherry-colored 3. Newspaperman Ochs 4. Easel part 5. Actress Turner 6. Ropes, as dogies 7. Place to put your feet up 8. Underskirt 9. First of three-in-a-row 10. Lower in public estimation 11. Onetime bowling alley employee 12. Threesome 13. English prince’s school 14. ’60s TV talk-show host Joe 18. Superannuated 23. Sewing shop purchase 25. TV’s Uncle Miltie 27. Short writings 29. Opponent 31. Likely 32. Actress Caldwell 33. End of the English alphabet 35. Trumpet 37. Ex-host Griffin 39. Black Halloween animal 40. French 101 word 41. Provider of support, for short 42. Much debated political inits 44. Sourpuss 47. Malign 50. “La Nausee” novelist 52. Sheiks’ cliques 54. Bemoan 55. Popsicle color 56. Bird of prey 58. 10 on a scale of 1 to 10 60. Family girl 62. Famous ___ 63. Something to make on one’s birthday 64. Regarding 65. Quite a story 66. Dublin’s land 69. ___ Victor 70. Hullabaloo
The answer is simple, yet very impressive. The crossword’s author, the mathematics professor Jeremiah Farrell, created the puzzle so that it could be solved in two different ways, revealing either “Clinton Elected” or “Bob Dole Elected” in the middle row. Many of the newspaper’s readers didn’t realize the prank and assumed New York Times was displaying a bias towards one of the candidates. They started sending lots of angry letters and calling the editor, complaining about arguably the coolest crossword of all time.
Six pawns are placed in the middle squares of the main diagonal of a chess board – b7, c6, d5, e4, f3, g2. You are allowed to take any pawn on the chessboard and replace it with two pawns – one on the square above it and one on the square on its right, in case there are empty squares there. If after several moves there are no more pawns on the main diagonal, show that all the squares above it except for h8 are covered by pawns.
SOLUTION
Assign the following weights on the squares of the chessboard:
1 on the main diagonal a8 – h1
1/2 on the diagonal b8 – h2
1/4 on the diagonal c8 – h3
1/8 on the diagonal d8 – h4
1/16 on the diagonal e8 – h5
1/32 on the diagonal f8 – h6
1/64 on the diagonal g8 – h7
Every time you make the splitting move, the total sum of the numbers of the squares covered by pawns remains a constant. At the beginning that sum is 6. Since 7/2 + 6/4 + 5/8 + 4/16+ 3/32 + 2/64 = 6, all 27 squares above the main diagonal, except the top-right corner (on which you can not place a pawn in any way), must be covered by pawns at the end.
If you know that the following game has been monochromatic, i.e. no piece has moved from black to white square or vice-versa, which one is the correct position of the bishop – e3 or e4?
SOLUTION
The correct position of the bishop is e3. Otherwise, no White’s piece could have captured the last Black’s piece, moving on black squares.