Solved cryptogram
Four colors will fill in any flat map so that no two regions along a border are alike.
Mathematics Facts, sourced to Wolfram MathWorld.
Solve it yourself
This fact is a cryptogram here: 68 letters over 21 different ones, graded hard.
Or go to the puzzle’s own page first.
What it means
Guessed by a student in 1852 and not settled until 1977, when Appel and Haken reduced the problem to a large but finite pile of cases and had a computer grind through them. It was the first major theorem whose proof no person could check by hand, and mathematicians argued for years about whether that counted. Three colors provably are not enough, so four is the answer rather than a comfortable bound.
The claim comes from Wolfram MathWorld.
- SourceWolfram MathWorld
- CollectionMathematics Facts
- Difficultyhard
- Length68 letters, 21 of them different
Nearby in the collection
The facts either side of this one.
- Wolfram MathWorldmedium, 70 letters
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About as hard as this one
Scored closest to it by the model behind our guide to solving cryptograms.
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