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.

You are allowed to enter the room only once (the bulb is not visible from outside). How can you determine which of the three switches turns on the light bulb?

turn one on for many hours, then turn ot back off and turn another one on. so we have one light on, one off but still warm and one off at room temperature.

Posted by theBal on 2002-05-16 07:33:30