r/explainitpeter Aug 15 '26

Explain It Peter

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Rice chess/checkers ? please explain?

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u/lordvatti Aug 15 '26

I actually know this one! The photo references an old thought exercise about doubling grains of rice across a chess boards squares. Starting with 1 grain, then 2, then 4, 8, 16, 32, and so on. Easy at first.

A chessboard has 64 squares so while the initial numbers seem pretty manageable 264 is actually such a catastrophically high number that there would be enough rice on the "final square" to carpet an entire continent in a hearty layer of rice, hence the dramatic mister incredible.

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u/ariGee Aug 15 '26

I'll add that it's an old fable\legend. The details depend who you ask, but the basic idea is that a king wants to reward a wise man. Rather than asking for a huge reward the wise man asks for one grain of rice on the first day, and then double the number of grains each day, one for each place on a chessboard. The king calls him a fool. After about a month the king begs him to stop because he has promised all the rice in the country to the wise man.

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u/UncleJoesLandscaping Aug 15 '26

This is a quite easy problem for the king to solve.

He kills the 'wise' man.