Escape From Elephantistan

Well, you’ve gone and murdered someone again. And this time you’ve done it in Elephantistan, which is renowned for its peculiar justice system.

The jury is divided, so you will decide your own fate. You’re presented with two urns, each of which contains 25 white balls and 25 black ones. Blindfolded, you must choose an urn at random and then draw a ball from it; a black ball means death, but a white one means you go free.

Tradition gives you the option to distribute the balls however you like between the two urns before you don the blindfold. This is thought to be a formality, as the total proportion of white balls to black does not change.

What should you do?

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Put one white ball in the first urn and the remaining 99 balls in the second. If you choose the first urn, you go free. If you choose the second, you have 49 chances out of 99, or nearly 50 percent. Altogether this strategy raises your chance of survival to nearly 75 percent. Adapted from George Gamow and Marvin Stern, Puzzle-Math, 1958.

February 11, 2010January 23, 2013 | Puzzles