2. 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

2. 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

It's something like this:
Turn two on for a while to let them warm up.  Then turn one of them off.  Run into the room.  One light bulb should still be on (the one where the switch is on).  Of the two that are still off, one will be warm (the one whose switch you flipped), and the other should be cold (the switch you didn't touch).