Logic Puzzle Forums 3 switches, one lightbulb
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#1
01-07-2013, 08:33 PM
 ephaliren Junior Member Join Date: Oct 2010 Posts: 9
3 switches, one lightbulb

ok, so here's the problem I mentioned earlier:

There is a room, with no windows and one door. There is no keyhole, and you cannot see under or around the edges of the door. The door is closed.

Inside the room there is an exposed incandescent light bulb. The light bulb is off.

Outside the room is a panel with three on/off switches. Only one switch will operate the light, the other two do nothing.

You must figure out which switch operates the light.

You are not allowed to dismantle anything (yes, someone asked about following the wiring…)

You may flip the switches on and off as many times as you want before you open the door, and there is no time limit.

You can only open the door once. Once you open it, you can no longer touch the switches and you MUST say which switch is the right one. (AKA no trying a switch, opening the door, trying the next switch, etc.) Once the door is open, you can go inside the room

So, how do you tell which switch operates the light?
#2
01-09-2013, 03:01 AM
 pinkgirl25 Junior Member Join Date: Dec 2012 Posts: 2

You could turn on the first one for two minutes and turn it off. Then the middle for two minutes and turn it off. Then the last and run inside. If it is on then it is the last is it. If the bulb feels hot then the middle one. If only warm then the first.

Or here is a better method...

Turn on the first one for like two minutes then turn it off. Then turn on the middle one run inside, if the light is on it is the middle one, if it is off feel bulb for warmth. If the bulb is warm then the first one turns on the light, if not then the last one does.

Is this right?
#3
01-09-2013, 04:11 PM
 ephaliren Junior Member Join Date: Oct 2010 Posts: 9

You are correct!
#4
01-27-2013, 09:16 PM
 pandalover10 Junior Member Join Date: Jan 2013 Posts: 1

i would watch under the door and see if there is a dim light under the door. right??

 Tags light bulb, puzzle, switches

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