Light Bulb

mattrick · Post by **mattrick** » Tue Dec 05, 2006 3:11 pm

You stand before 3 lightswitches. One of these switches is able to turn on/off a lightbulb in a room nearby.

You can't see in the room but you know the light was turned off all day.

You have to find which switch is connected to the lightbulb.

In order to find the switch that is connected to the lightbulb, you can do only the following:

Step 1: Use zero or more switches as much as you want.

Step 2: Go to the other room.

Step 3: Tell which switch is connected to the bulb without exiting the room.

You cannot go back to the switch room and only get one attempt.

Istenem · Post by **Istenem** » Tue Dec 05, 2006 4:21 pm

my brain hurts but how about this:

turn on switch A, leave it on for a few minutes then flick the same switch to turn it off. immediately flick switch B and go into the room.

if the bulb is on it is switch B, if the bulb is off but warm it is A, if it is off and cool it is switch C.

mattrick · Post by **mattrick** » Tue Dec 05, 2006 4:45 pm

unknownpseudonym wrote:my brain hurts but how about this:

turn on switch A, leave it on for a few minutes then flick the same switch to turn it off. immediately flick switch B and go into the room.

if the bulb is on it is switch B, if the bulb is off but warm it is A, if it is off and cool it is switch C.

Very good UP!!