Tag Archives: Invariants Puzzles

Puzzle #195: 1989!

Posted on September 10, 2017 by Alok Goyal

This is a beautiful puzzle from Mathematical Circles (Russian Experience) by Dmitri Fomin, Sergey Genkin and Ilia Itenberg. There numbers 1, 2, 3, ….. , 1989 are written on a blackboard. It is permitted to erase any two of them … Continue reading →

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