Heart and Head

Just offering this as a curiosity:

ohnishi cryptarithm

It was devised by the late Japanese cryptogramist Kyoko Ohnishi, and praised by puzzle maven Nob Yoshigahara. If each letter stands for a unique digit, what product is encoded here?

When this appeared in MIT Technology Review in November 2012, it attracted 20 responses, but it appears that all of them used computers to find the solution. If there’s a way to reason it out, I don’t think anyone has found it yet.

If we assume that neither of the factors has a leading zero, and that the partial products have five and four digits, as shown, then the solution is unique. I’ll put it in the spoiler box below, in case you want to work on it yourself.

Click for Answer

Black and White

techritz problem

By M. Techritz. Place the black and white kings on the board so that White can mate in one move.

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In a Word

n. enrichment

adj. unprofitable

Another puzzle by Yakov Perelman:

“Two fathers gave their two sons some money. One gave his son 150 rubles and the other 100 rubles. When the two sons counted their finances, they found that together they had become richer by only 150 rubles. What is the explanation?”

Click for Answer



Russian science writer Yakov Perelman asks: How many times must an 8-toothed cogwheel rotate on its axis to circle around a 24-toothed cogwheel?

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Black and White

tanner chess problem

By John Tanner. White to mate in two moves.

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Nobody Home

pooh and piglet

A puzzle by S. Sefibekov:

Winnie-the-Pooh and Piglet set out to visit one another. They leave their houses at the same time and walk along the same road. But Piglet is absorbed in counting the birds overhead, and Winnie-the-Pooh is composing a new “hum,” so they pass one another without noticing. One minute after the meeting, Winnie-the-Pooh is at Piglet’s house, and 4 minutes after the meeting Piglet is at Winnie-the-Pooh’s. How long has each of them walked?

Click for Answer

Bright and Early

Meteors are more commonly seen between midnight and dawn than between dusk and midnight. Why?

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Black and White

ropet chess problem

By Ivan Pavlovich Ropet. White to mate in two moves.

Click for Answer

Podcast Episode 69: Lateral Thinking Puzzles


Here are four new lateral thinking puzzles to test your wits! Solve along with us as we explore some strange situations using only yes-or-no questions.

Puzzles 1 and 2 are from Kyle Hendrickson’s 1998 book Mental Fitness Puzzles and Jed’s List of Situation Puzzles.

Thanks to listeners Saber and Tommy Honton for puzzles 3 and 4. Here are two corroborating links — these spoil the puzzles, so don’t click until you’ve listened to the episode:

Puzzle #3

Puzzle #4

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Black and White

legentil chess problem

By Georges Legentil. White to mate in two moves.

Click for Answer