You are in a room with three switches that control three light bulbs in another room. You can only enter the other room once, and you cannot see the light bulbs from the first room. How can you figure out which switch controls which light bulb?
Solution: You can turn on two switches and leave them on for a few minutes, then turn off one of them and enter the other room. The light bulb that is still on is controlled by the switch that is still on. The light bulb that is off but warm is controlled by the switch that you turned off last. The light bulb that is off and cold is controlled by the switch that you never turned on.
