You enter a room with three light switches on the wall, all currently in the OFF position. Through a closed door are three light bulbs in another room, corresponding to each switch. You can flip the switches however you like, but you may only open the door and look at the bulbs once. How can you determine which switch operates which bulb?
Turn Switch 1 ON and leave it for 10 minutes. Then turn Switch 1 OFF and turn Switch 2 ON immediately. Leave Switch 3 OFF. Enter the room.
The bulb that is ON belongs to Switch 2. The bulb that is OFF but warm to the touch belongs to Switch 1. The bulb that is OFF and cold belongs to Switch 3.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Medium. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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