You’re locked in a room with three light switches and a closed door. On the other side of the door, there are three light bulbs. Once you open the door, you cannot touch the switches again.
How can you be certain which switch controls which light bulb?
Show Answer
Switch on two of the switches and leave them on for a couple of minutes. Then, switch off one of the switches (leaving one switch still on). Go through the door. The bulb that is still on is controlled by the switch left on and the bulb that is warm to touch is controlled by the switch you just switched off. The third bulb (the cold one) is controlled by the switch you didn’t touch.
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