Bulbs and Switches

There are three bulbs on 19th floor and there are three switches X, Y and Z on the ground floor. Each switch belongs to one bulbs, not necessarily in order. You can switch on or off as many times you want but you can go on 19th floor only once.

How will you find out which swich belongs to which bulb? Note that you are the only person over there. You can't go outside and can't use any tools.








Answer :
switch X on and leave for 5 minutes. The turn that on off. switch Y on then go up to 19th floor. X switches the lightbulb that is warm but off, Y the one that is lit and Z the cold lightbulb that is off. Pretty simple huh....

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