March 18th, 2006 at 08:33pm Posted by Bill
See if you can solve this brain teaser:
The setup: You are at the entrance of a large house. At the far end of the house is an empty room with a single light bulb. The door to this room is closed, allowing no light to escape. On the wall next to you are three standard on/off electrical switches. One of these three switches turns the bulb on and off. The other two switches do nothing.
The goal: You must determine which one of the three switches controls the bulb.
The limitation: You can only make one trip to the room with the bulb, and you can’t come back to the light switches once you are in the room. Before you go to the room, however, you can do whatever you like to the switches (without disassembling, of course: no cheating!), and you can take as much time as you like.
So, what would you do? How exactly would you determine which of the three switches controls the bulb? Post your guesses and questions as a comment, and I’ll do my best to respond quickly. I’ll post the answer next Saturday.
6 Comments Add your own
1. tabitha jane | March 21st, 2006 at 3:42 pm
flick two light switches up at once . . . walk into the room . . . if the light is still off, then i know the switch i didn’t flick is the correct switch.
if that doesn’t do the trick. i’m screwed.
2. Bill | March 21st, 2006 at 5:38 pm
You’re warm. However, if the light bulb is still on, you don’t know which of the two switches is the one.
Another guess, maybe?
3. Justin Collins | March 24th, 2006 at 8:28 am
Open the door and dont go in letting you see if the light is on or off
4. Justin Collins | March 24th, 2006 at 8:38 am
ok turn on switch a and b for a while then turn off a go into the room if the bulb is on then its b if its off and warm its a if its off and cold its c
5. Bill | March 24th, 2006 at 10:16 pm
Yay, we have a winner. Justin is right. Here is the answer I had ready to post tomorrow night if no one figured it out:
“Turn all three switches off, wait five minutes.
Turn switch #1 on, wait five more minutes.
Turn switch #1 back off, turn switch #2 on, and run into the room.
If the bulb is on, you know switch #2 controls it.
If the bulb is off, touch the bulb with your hand.
If it is warm, switch #1 controls it.
If it is cold, switch #3 controls it.”
6. rebecca marie | March 27th, 2006 at 9:33 am
i googled it, so i didn’t post the answer. i’m a cheater.
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