You're in a room with three switches: A, B and C.
One of these switches is connected to a light bulb in another room; the other 2 switches are fake.
How can you tell which switch operates the bulb when you are only allowed to flick the switches once? i.e. you flick the switches into whatever position you want. Then when you're happy, you leave the room and walk down the corridor into the room with the light bulb in (once you leave the room with the switches, you are not allowed to go back in
). You note the state of the bulb and determine which switch operates the bulb.
Note that you are not allowed to dismantle the switches, or tamper with them in any way whatsoever (this is to prevent you from testing the circuits with an electrical screwdriver for example).
When you flick the switches you cannot see the light bulb or the light from the bulb - there are 2 closed doors between you and the light bulb (with no gaps under the doors, etc
It's not too difficult this one, so I thought I'd post it in the easy section (plus I wanted to be the first to post in here