You're standing at three light switches at the bottom of stairs to the attic. Each one corresponds to one of three lights in the attic, but you cannot see the lights from where you stand. You can turn the switches on and off and leave them in any position. How can you identify which switch corresponds to which light bulb if you are only allowed one trip upstairs?
6 comments:
You may not be able to see the “lights” from where you are, but at night, you could probably see the illumination if you left the attic door open and switches were on. So make one trip to the attic during the day with three different color light bulbs, red, blue and yellow. Replace the current light bulbs with the color light bulbs and make a notation where you installed each bulb. At night, turn on one switch at a time and watch for the illumination color and match up the switch to the location.
That's a pretty good answer. However, you can't see the lights from where you stand. Can you come up with anything else?
Okay, here is the answer:
Turn on the first two switches and leave them on for 5 minutes. After 5 minutes, turn off the second switch, leaving the first switch on. Now go upstairs to the attic. The light that is on is connected to the first switch. A light that is off but has a bulb that is still warm to the touch is connected to the second switch. The light that is both off and cold to the touch is connected to the third switch, which was never turned on.
OH! I thought about this one for a long, long time. I even tried to act it out. Damn it.
I thought about it for a long time, too. Then I thought, who cares which one turns on what? As long as the light is on when I go up there, I'm cool.
NEISHA is a riot!!!!
Why did you give the answer before we even had time to answer it? Not sure if I would have thought of it though.
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