Sunday, March 6, 2011

Which Switch control The Bulbs

A windowless room contains three identical light fixtures, each containing an identical light bulb. Each light is connected to one of three switches outside of the room. Each bulb is switched off at present. You are outside the room, and the door is closed. You have one , and only one, opportunity to flip any of the external switches. After this, you can go into the room and look at the lights, but you may not touch the switches again. How can you tell which switch goes to which light?

The consensus of opinion seems to be this:

Switch on switch number 1, wait a few minutes and switch on switch number 2.

Enter the room and which ever bulb is on and is hot is connected to switch 1, whichever is on and cold is connected to switch number 2, and the remaining bulb is connected to switch number 3.

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