You are standing outside a closed room. The only entrance in is a door. Inside the room are 3 lights, each on a different wall. Outside the room next to the door are the 3 switches to those 3 lights. Each switch controls only one light, each a different light. No light escapes under the door when the lights are turned on. There are no windows, there is a ceiling. You can't see inside from the outside. You will be allowed to go into the room only one time and close the door behind you.
You need to determine which switch controls which light from outside the room.
Go.
(there is no need to disassemble the switch fixture)
I know the answer too. Should I post it? Okay I suppose I will - people can always stop reading if they want to try to get it themselves.
The Answer is Below
Turn on one light for 15 minutes. Then turn it off and turn on another light.
Walk into the room. The light that's on is controlled, obviously, by the last switch you turned on. The warm light (that's off) corresponds to the light you left on for 15 minutes. The cold light that's off is for the switch you never touched.
Our professor in one of my business classes (11+ years ago) posed this riddle to a class and had everyone break into discussion groups and come up with solutions.
There were several off-the-wall suggestions as I remember. One was to enter the room and have a friend close the door and manipulate the switches while you logged which light. It was decided that breaks the rules.
The consensus best solution was to turn on each in turn for an equal period of time and then go into the room and feel the lightbulbs. Temperature would tell which switch controlled which bulb.
November 29th, 2004, 11:43 AM
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