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 Which Switch Operates Which bulb?
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TchrWill
Advanced Member

USA
80 Posts

Posted - 05/15/2013 :  09:45:12  Show Profile  Reply with Quote
Assuming that you just haven't had time to explore the 6 Pointed Star problem, here is another non-math problem to chew on for a breather.

You are in one room with three light switches. In an adjacent room there are three light bulbs operated by the three switches in the first room. One switch operates one bulb. You have no knowledge of which switch operates which bulb. You can open a door and enter the room with the three light bulbs only once. How is it possible to determine which switch operates which bulb?

Enjoy
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the_hill1962
Advanced Member

USA
1469 Posts

Posted - 05/15/2013 :  10:32:16  Show Profile  Reply with Quote
I was stumped on this one. It is "mathematically" impossible isn't it?
The need to know the answer got the best of me and I had to look it up!
I doubt if I would have come up with the solution without looking it up.
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TchrWill
Advanced Member

USA
80 Posts

Posted - 05/15/2013 :  10:59:55  Show Profile  Reply with Quote
Regarding "I was stumped on this one. It is "mathematically" impossible isn't it?" Which one are you referring to; the 6 pointed star or the switch/bulb one? Will be glad to post my solutions if you are interested.Both are possible.
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the_hill1962
Advanced Member

USA
1469 Posts

Posted - 05/16/2013 :  09:46:57  Show Profile  Reply with Quote
It has been a long time since I have heard of the 6 Pointed Star problem and I forget what it is.
As for the switch/bulb, the solution is not "mathematical". The only solution that I see is to flip on a switch and leave it on for a few minutes and then, immediately after flipping it off, flip on a different switch and quickly go into the room and feel which of the two unlit bulbs is warm. The warm one belongs to the first switch you flipped on for a few minutes and the cooler one belongs to the switch that you didn't touch. The lit bulbs obviously belongs to the switch that you left flipped on.
That solution assumes that you started with all switches off in the first place. I think it would also work if all the switches were on at the start but I haven't thought that through. It would sort of be like the opposite with the "feel" of the temperatures.
Now, LED lights don't produce heat so if the bulbs were LED, I don't know how it would be solved.
quote:
Originally posted by TchrWill

Regarding "I was stumped on this one. It is "mathematically" impossible isn't it?" Which one are you referring to; the 6 pointed star or the switch/bulb one? Will be glad to post my solutions if you are interested.Both are possible.

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TchrWill
Advanced Member

USA
80 Posts

Posted - 05/17/2013 :  09:01:10  Show Profile  Reply with Quote
You got it.
Lets see "watt" we can come up with.

Label the switches 1, 2, and 3.

1--Turn switch #1 on for a minute or so, then turn it off.
2--Turn switch #2 on and enter the room.
3--Immediately feel each light to see which one is warm.
4--Having found the light that is warm to the touch, you have found the light that is controlled by switch #1.
5--Obviously, the light that is on when you entered the room is the light controlled by switch #2.
6--The remaining light is the one controlled by switch #3.

As for the star solution, see the star thread.


Edited by - TchrWill on 05/17/2013 09:05:15
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