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Puzzle 5) Bulbs and Switches

Submitted by Abhishek Jain, on August 05, 2017


Suppose you are in a room with 3 switches. In next to room there are 3 bulbs (in off state), each switch is link to some bulb. It is impossible to see from one room to another. Your task is to find out, which switch stand to which bulb, if you may enter the bulb room exactly once.

Important points of puzzle:

  1. There are 2 rooms one with 3 switches and other one with 3 bulbs.
  2. All bulbs are off at that moment.
  3. It is guaranteed that each switch belongs to a bulb.
  4. It is impossible to see from one room to another.
  5. Our task is to identify which switch belongs to which bulb.
  6. Condition: You can visit the room with bulbs exactly once.


Keep the first bulb switched on for few minutes. It gets heated and its tungsten wire becomes red hot and then all you have to do is …switch it off, switch on the another bulb, go to the room with bulbs, see them and tell which one was switched on as the first one (the redhot) and the others can be easily identified as one is on and other one is off.

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