You are looking round an empty house with 2 floors. At the bottom of the stairs are the light switches for the hanging bulb in the room upstairs, however there is a door which no light can get past separating upstairs from downstairs.

 

The switch console is actually 3 switches - one of which is connected to the upstairs light, the other 2 aren't connected to anything.

 

You can switch the switches in any combination as much as you like, but you can only go upstairs to see the result once.

 

How do you guarantee that you find out the correct switch for the light?

 

Theres no windows etc or any other way to actually*see* the light from upstairs, downstairs.

 

Pete :D

PMSL:rofl: :rofl: :rofl: :dance:

Flick switch 1 and leave it on for a few minutes.

Switch 1 off and 2 on.

Now go upstairs and check the light.

 

If it's on, the answer's 2.

If it's off, but the bulb's still hot, the answer's 1.

If it's off and the bulb's cold, the answer's 3.

 

:D

bastard!

 

:D:D

ah beat me too it, but only because I've heard this one before.