3 Lights
Published: Nov 30, 1999
Riddle: In the basement there are 3 light switches in the off position. Each switch controls 1 of 3 light bulbs on the floor above. You may flip any of the switches, but you may only go up stairs one time. How can you determine which switch controls each light?
Answer: Flip any one switch to the on position for 5 minutes. Then flip that switch off. Quickly flip any other switch to the on position and run up stairs. Feel the two lights that are off. One of them will be hot because it was on for 5 minutes. Obviously the hot bulb is controlled by the first switch you flipped on. The light that is currently on is controlled by the switch you last flipped on. The cold bulb that is off is controlled by the only switch left. When solving problems we often need to use all our senses.
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