### Riddle: 5 lights

This is an update to the post: http://fulldecent.blogspot.com/2009/01/profile-riddle-is-back-lights.html

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The riddle has so far received no correct answers (several people responded with the obvious "cop out" answer). Therefore, this is being declared the hardest riddle yet. I am upgrading the bounty to 2 points for a correct answer! Also, I am making the riddle a little harder...

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.

This is very difficult. So remember, you are encouraged to Google around for similar riddles and to ask your friends. Cheating is encouraged!

Tyler McHenry said…
I'm not sure if this counts as a cop-out answer (and this obviously wouldn't work with CFL bulbs, but then again neither would the 4-bulb solution) but:

Chose 1 switch. Flick it on and off continuously for a good, long while (say, a few days), or alternatively leave it on for a very long time (like, a year or two). The point is that the problem specifies no time limit.

Once you've done that, then with the remaining four switches do the same thing as with the four-switch problem. Turn two switches on for a few minutes, then turn one of them off and turn another on. Quickly enter the room and feel the bulbs.

You should be able to differentiate the last four bulbs between on/hot, on/cold, off/hot, off/cold as with the four-switch problem. The fifth bulb, the one with the broken filament, is the first one you chose.
Will Entriken said…
Thank you for your submission. I saw a another solution like from Duncan this and considered whether the underlying assumption is valid: after turning on, a bulb does not get hot immediately.

Previously I thought this assumption fails and even tested it. However, now I see that for lower watt bulbs it is true! Naturally, valid assumptions are given to contestants, and Duncan retroactively gets his point.

You, sir, are however WAY past the deadline.

FYI the cop out answer was: the switches are labeled.