You are inside a room and there are exactly three electric bulbs outside of the room. The three bulbs have their corresponding switches (exactly three) inside the room. You can turn the switches on and off and leave them in any position. How would you identify which switch corresponds to which electric bulb, if you are allowed to go outside and come inside the room only once?

This is a logic puzzle, which was asked to me by a friend during a general conversation few weeks ago. At that time neither I could figure nor he told me the solution. Finally, I have found a satisfactory answer to this puzzle, which is off-course shareable.

Now if you think  you’re smart enough to solve it, then post  your answer in the comment-box without opening the solution page or searching the web. 🙂

Published by Gaurav Tiwari

A designer by profession, a mathematician by education but a Blogger by hobby. With an experience of over seven years with WordPress, PHP and CSS3, Gaurav is capable of doing almost anything related to these. Beyond that, He is a mathematics graduate & a civil service aspirant.


  1. you turn switch number 1 on and leave it on for a few minutes, then turn it off. Then flip # 2 on, and leave 3 off. Exit the room to see the bulbs. The light that is on is switch # 2. The light that is off, but warm, is switch #1. The one that is off and not warm, is #3.

    Good puzzle. It took me a few minutes.


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