Friday 9 December 2016

3 switch and light puzzle asked in interviews

3 switch puzzle 

 There are three switches outside the room . 

 Two Of which are useless , while one is connected to a lightbulb inside the room.

 You can on or off any switch any number of time (it also cover you can on or off any number of switch together) .

 You have one, and only one, opportunity to go inside the room and look . 

 Question is : How can you tell which switch goes to light?


  1. switch on the second switch for five minute and then switch it off and then immediately switch on 3rd one and enter the room. Touch the bulb:
    1> if buld is on then 3rd switch.
    2> if the buld is off but is hot then second switch.
    3> if the bulb is off and is cold first switch

  2. I go out side 1switch on on 5 min and off the switch
    And on 2nd switch
    And gi in room
    When bulb is shine
    So 2 switch is connected to bulb
    When bulb is not shine but hot
    So 1 switch is connected to bulb
    When bulb not shine and not hot
    So 3 switch is connected to bulb


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