1997, pp 177-190

The Power of the Pigeonhole

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Abstract

Can you prove that a large number of people in the U.S. have exactly the same number of hairs on their head? And what does this question have in common with the following problem? In a bureau drawer there are 60 socks, all identical except for their color: 10 pairs are red, 10 are blue, and 10 are green. The socks are all mixed up in the drawer, and the room the bureau is in is totally dark. What is the smallest number of socks you must remove to be sure you have one matching pair?