Solved cryptogram
When everyone in a room shakes hands once, the number of handshakes is a triangular number.
Mathematics Facts, sourced to Wolfram MathWorld.
Solve it yourself
This fact is a cryptogram here: 74 letters over 21 different ones, graded hard.
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What it means
With five people each shakes four hands, which counts twenty, but every handshake has been counted from both ends, so the answer is ten. In general it is a number times the one below it, halved. Those are the triangular numbers, one, three, six, ten, fifteen, the counts of dots you can stack into a triangle. Gauss is said to have found the same formula as a schoolboy, told to add the numbers up to a hundred.
The claim comes from Wolfram MathWorld.
- SourceWolfram MathWorld
- CollectionMathematics Facts
- Difficultyhard
- Length74 letters, 21 of them different
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