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Showing posts from February, 2009

Riddle: 5 lights - answer

The original riddle was:

You are outside a room with 5 light switches. You cannot see in the room. You don't have anyone else to help you. You enter the room. Inside the room are 5 lights. You then find out which light switch controls which light. And here, finally, is the "correct" answer:

While outside the room, you use the switches. You turn 1 and 2 on, 3 off. Then you turn switches 4 and 5 on and off, on and off, on and off very fast for 10 minutes. Finally, you set switch 2 and 5 off and 4 on:

BeginninngAfter 10 minutes...Switch 1OnOnSwitch 2OnOffSwitch 3OffOffSwitch 4On, off, on, off...OnSwitch 5On, off, on, off...Off
Then you enter the room and look for the light that is off, but hot -- this is light 2. Find the light that is on -- this is light 1. Remove the remaining bulbs from the sockets and jiggle them. Two of them have burned out -- the other one is light 3. Put light 3 into one of the remaining sockets. If it lights up, this is light 4, if it doesn't, th…