Rich's Which Switch?

[Richard Priest]

This was given to me by a friend -

In a house, one room has 3 light switches, one of which (and only one) switches on the lights in the room next to it.You can only go into the adjoining room once.How are you going to work out which one of the 3 switches controls the lights in the next room?

No prizes I'm afraid.

[Jon O'Neill]

If I assume that one of the switches also works the light in the first room, I think I can do it. Is that a reasonable assumption?

[Richard Priest]

Not really on the right lines there Jono, sorry mate.

[Ian Volante]

Leave the door open while you flick each switch in turn. Conversely, go into the other room and reach round to the switches.

As a real answer however:

Turn on switch 1 for a while. Turn it off again, then turn on switch 2 and leave it on. Go into the other room and if the light isn't on, check if it is warm. Warm =1 switch 1, on =2 and otherwise it's 3.

[Phil Makepeace]

Wasn't this one of the tasks that Derren Brown used to determine who he picked in his Russian Roulette stunt? It's a cute solution.