Puzzles & Games Do you see the light - Solved

Discussion in 'Puzzles & Games' started by kiwirobin, Feb 1, 2005.

  1. kiwirobin

    kiwirobin Premium Member

    A light bulb is hanging in a room. Outside of the room there are three switches, of which only one is connected to the lamp. In the starting situation, all switches are 'off' and the bulb is not lit.

    The Question: If it is allowed to check only once to see if the bulb is lit or not (this is not visible from the outside), how can you determine which of the three switches turns on the light bulb?

    [Edited on 2-4-2005 by kiwirobin]

    [Edited on 2-4-2005 by kiwirobin]
  2. Bleys

    Bleys Phoenix Takes Flight Staff Member


    I have to think about this one for a while.

  3. mscbkc070904

    mscbkc070904 Premium Member

    Electrical connection that fires from the switch being turned up, wait a minute...hmmm I thought I knew the answer but something is not quite, adding up there.

  4. drlau

    drlau Premium Member

    Nice one! :up:

    The solution

    3 switches - A, B, and C

    Step 1: Turn ON both A and B.

    Step 2: Wait a few minutes, then turn OFF only B.

    Step 3: Go into room. If the light is on, switch A controls it. If the light is off, feel the bulb. If it is hot, then switch B controls it. If it is cold, switch C controls it.

    :lb: :lb: :lb: :lb: :lb:
  5. kiwirobin

    kiwirobin Premium Member

    You got it drlau:hail: