Since the long January break is coming to an end, let me post this next one a tad early. This problem seems to be folklore. Thanks to Dan Velleman for suggesting it.
You are blindfolded and face a large pile of coins on a table. You are told that 877 of them are heads up. Show how you can divide the coins into two groups so that each group created has the same number of heads showing.
Note: Of course, you cannot see the coins, nor can you distinguish heads or tails by feel.
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"Invisible Handshake", the recently completed giant snow sculpture of a Costa surface by Helaman Ferguson, Dan Schwalbe, Tamas Nemeth, and me, can be seen at:http://mupperg.math.macalester.edu:81/faculty/schwalbe/wwwroot/colorado99/
This was part of the ninth annual Breckenridge International Snow Sculpture Championships, just held in Breckenridge, Colo.© Copyright 1999 Stan Wagon. Reproduced with permission.