Saturday, March 8, 2008

Lightswitch puzzle

There are three switches on the wall outside a room. (Four, for the more ambitious.) Exactly one of them controls a lightbulb inside the room. You are allowed to change the switches as much as you want, after which you may enter the room only once and see the lightbulb. Then you must say which switch controls the light.

This puzzle is not probabilistic. There is a solution that gives the correct answer 100% of the time.

This post's theme card game: Bang! I, the sheriff, was killed this evening by one of my misguided deputies in the hurried speed-round we did as we were being kicked out of a closing building. So the outlaws won. In retribution, I left them all befuddled by this puzzle.

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