There is a room with 3-bulbs inside and the switches are outside the room.
You make any combination of three switches and enter room only once.
How do you find out the respective switches for these three bulbs

Question

There is a room with 3-bulbs inside and the  switches are outside the room. 
You make any combination of three switches and enter room only once. 
How do you find out the respective switches for these three bulbs

anonymous · Answer

Turn switch #1 on for 30 minutes, then turn it off.
Then turn switch #2 on and enter the room.

You will see one light turn on, that one is controlled by switch #2.
You will see two lights turned off - touch them, one in warm because it's been on for 30 minutes. 
The warm one is controlled by the switch #1.
The bulb that is off and cold is controlled by switch #3.