Puzzles

Black and White

ferber chess problem

By Eugène Ferber. White to mate in two moves.

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The Froggy Problem

Speaking of Lewis Carroll — and further to Wednesday’s logic exercise — here’s the king of all Carroll’s logic problems. What’s the strongest conclusion that can be drawn from these premises?

  1. When the day is fine, I tell Froggy “You’re quite the dandy, old chap!”
  2. Whenever I let Froggy forget that 10 pounds he owes me, and he begins to strut about like a peacock, his mother declares “He shall not go out a-wooing!”
  3. Now that Froggy’s hair is out of curl, he has put away his gorgeous waistcoat.
  4. Whenever I go out on the roof to enjoy a quiet cigar, I’m sure to discover that my purse is empty.
  5. When my tailor calls with his little bill, and I remind Froggy of that 10 pounds he owes me, he does not grin like a hyena.
  6. When it is very hot, the thermometer is high.
  7. When the day is fine, and I’m not in the humor for a cigar, and Froggy is grinning like a hyena, I never venture to hint that he’s quite the dandy.
  8. When my tailor calls with his little bill and finds me with an empty pocket, I remind Froggy of that 10 pounds he owes me.
  9. My railway shares are going up like anything!
  10. When my purse is empty, and when, noticing that Froggy has got his gorgeous waistcoat on, I venture to remind him of that 10 pounds he owes me, things are apt to get rather warm.
  11. Now that it looks like rain, and Froggy is grinning like a hyena, I can do without my cigar.
  12. When the thermometer is high, you need not trouble yourself to take an umbrella.
  13. When Froggy has his gorgeous waistcoat on, but is not strutting about like a peacock, I betake myself to a quiet cigar.
  14. When I tell Froggy that he’s quite a dandy, he grins like a hyena.
  15. When my purse is tolerably full, and Froggy’s hair is one mass of curls, and when he is not strutting about like a peacock, I go out on the roof.
  16. When my railways shares are going up, and when it’s chilly and looks like rain, I have a quiet cigar.
  17. When Froggy’s mother lets him go a-wooing, he seems nearly mad with joy, and puts on a waistcoat that is gorgeous beyond words.
  18. When it is going to rain, and I am having a quiet cigar, and Froggy is not intending to go a-wooing, you had better take an umbrella.
  19. When my railway shares are going up, and Froggy seems nearly mad with joy, that is the time my tailor always chooses for calling with his little bill.
  20. When the day is cool and the thermometer low, and I say nothing to Froggy about his being quite the dandy, and there’s not the ghost of a grin on his face, I haven’t the heart for my cigar!

Unfortunately, Carroll died before he was able to publish the solution — but he warned that it contains “a beautiful ‘trap.'”

Made to Order

1. Find an expression for the number 1 that uses each of the digits 0-9 once.
2. Do the same for the number 100.
3. Write 31 using only the digit 3 five times.
4. Express 11 with three 2s.
5. Express 10 with two 2s.
6. Express 1 with three 8s.
7. Express 5 with two 2s.

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Animal Behavior

A logic exercise by Lewis Carroll. What conclusion can be drawn from these premises?

  1. Animals are always mortally offended if I fail to notice them.
  2. The only animals that belong to me are in that field.
  3. No animal can guess a conundrum unless it has been properly trained in a Board-School.
  4. None of the animals in that field are badgers.
  5. When an animal is mortally offended, it rushes about wildly and howls.
  6. I never notice any animal unless it belongs to me.
  7. No animal that has been properly trained in a Board-School ever rushes about wildly and howls.
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Query

How are the following numbers arranged?

0, 2, 3, 6, 7, 1, 9, 4, 5, 8

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Dog’s Mead

dog's mead puzzle

This puzzle was devised by W.T. Williams. The goal is to discover the age of Father Dunk’s mother-in-law (2 down), but the clues contain so much cross-reference and the grid so many interlocking solutions that practically the whole puzzle must be completed to find it.

The year is 1939. There are 20 shillings in a pound; 4840 square yards in an acre; a quarter of an acre in a rood; and 1760 yards in a mile.

ACROSS

1. Area in square yards of Dog’s Mead
5. Age of Martha, Father Dunk’s aunt
6. Difference in yards between length and breadth of Dog’s Mead
7. Number of roods in Dog’s Mead times 8 down
8. The year the Dunks acquired Dog’s Mead
10. Father Dunk’s age
11. Year of Mary’s birth
14. Perimeter in yards of Dog’s Mead
15. Cube of Father Dunk’s walking speed in miles per hour
16. 15 across minus 9 down

DOWN

1. Value in shillings per rood of Dog’s Mead
2. Square of the age of father Dunk’s mother-in-law
3. Age of Mary, father Dunk’s other daughter
4. Value in pounds of Dog’s Mead
6. Age of Ted, father Dunk’s son, who will be twice the age of his sister Mary in 1945
7. Square of the breadth of Dog’s Mead
8. Time in minutes it takes Father Dunk to walk 4/3 times round Dog’s Mead
9. The number which, when multiplied by 10 across, gives 10 down
10. See 9 down
12. Addition of the digits of 10 down plus 1
13. Number of years Dog’s Mead has been in the Dunk family

Hint: Start with 15 across, and keep your wits about you — most of the clues require some sort of insight or intelligent narrowing of the possible solutions; there’s very little mechanical plugging of numbers. With enough careful, dogged reasoning, it’s possible to complete the entire grid, but it’s stupendously hard.

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Black and White

carpenter chess problem

By Paud D. Carpenter. White to mate in two moves.

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Emptied Nest

Solve for x:

emptied nest problem

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Black and White

palitzsch chess problem

By Friedrich Martin Palitzsch. White to mate in two moves.

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Short-Handed

Suppose we have a clock whose hour and minute hands are identical. How times times per day will we find it impossible to tell the time, provided we always know whether it’s a.m. or p.m.?

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