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Puzzle – Switches

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There are three switches outside a room, all in the “off” position. One of the switches controls a light bulb inside the room, but you don’t know which one. You are allowed to enter the room only once, and you cannot turn the switches on or off while you are in the room. How can you determine which switch controls the light bulb?

Puzzle – Switches


Turn on the first switch and leave it on for a few minutes. then, turn off the first switch and turn on the second switch. Enter the room and there will be three possible scenarios:

  • If the light bulb is on, it is controlled by the second switch.
  • If the light bulb is off but warm to the touch, it is controlled by the first switch.
  • If the light bulb is off and cool to the touch, it is controlled by the third switch.
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Last Updated : 19 Apr, 2023
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