You’re in the basement of a three story house. Three light switches are in the basement, one of which controls a light on the second floor. You can only make one trip up to the second floor to determine which switch controls the light.
How do you determine which switch controls the light?
Answer after the jump. Think it through, take your time.
No cheating.
Choose any switch, and turn it on for 1 minute. Turn it off, and select another switch. Walk upstairs to the second floor. If the light is off, but the bulb is warm, the first switch controls the light. If the light is on, the second switch controls the light. If the light is off, and cool, the third switch controls the light.
Who got it right?
Forget about that: iPods to the BATTLEFIELD!
and some us thought using xbox controllers in the field was freakin’ genius…:)
(Threadjacking to give all the macophiles around here a fix)
What happens if the lightbulb is florescent? It doesn’t get warm.
You wish it doesn’t get warm.
This riddle makes Al Gore sad.
Me too – but just because I didn’t figure it out.
As an inherently lazy person, my solution was to quickly give up and read the instructions.
My answer was to have one of my sons wait on the second floor and yell down to me when the light’s on.
Or you could use the Hornet-driver method of troubleshooting: gripe the aircraft and head for the club.
Isn’t that the old joke: “RADAR inop when O-F-F/O-N switch in O-F-F position”?
See, I read the phrase “You can only make one trip up to the second floor” as also meaning “…but you can make as many trips to the third floor as you like.” If you do it that way, it’s pretty easy.
‘Course, I guess Lex’s answer would work, too… if you’re an “inside-the-box” kinda thinker.
Major, given that a trip to the third floor implies passing through the second floor, I did take that as a constraint. No mention was made of the first floor, however.
More importantly, upon which floor is the liquor cabinet?
– Max
The quiz didn’t say why I was engaging in this exercise, so I took the easy way out.
Turn on switches one at a time until, looking up the stairwell, I can see the light on the first floor (or I can walk up there, that option is not defined). Tag that switch. With any one of the remaining switches turned on, climb stairs and determine if second or third floor light is lit. Return to basement and tag remaining switches.
“But Max, what if there’s no stairwell?”
Then how did I get there?
“Maybe there’s an elevator?”
Then maybe I hit the fire key on the elevator and look up the shaft to see which floor is lit?
“No, no, you’re not doing this right. It’s a puzzle, have fun with it.”
Holding a mirror out the basement window?
“sob!”
Yeah, I was kind of hard on teachers when it came to story problems.
– Max
I like the cut of your jib, Max.
I’d fire the electrical contractor.
I would buy 40-11 extension cords with light bulb socket connectors, plug them into every single light in the house, run them down to the basement after carefully tagging and numbering them, hook each to a light bulb bearing receptacle (lamp) in the basement and then flip each switch, take notes.
Or. I could just dump all the cords into a tub in the basement, fill it with water and pirates and flick the switches. Yes. That’s it.
Would I blow a fuse if I did this? If I had a hundred $, how many times could I afford to do this if it was a 30 amp fuse?
If you contact the Saudi’s they will provide a limitless supply of fuses. The last ransom they paid was $3 million. The Italians and French might pitch in for the bathtub.
I guess I’m really screwed up. I assumed that since there were three floors and three switches, that each controlled a light on each floor. Since you are in the first floor (basement), you can eliminate one switch. Turn on one of the two remaining switches, then go to the second floor. If it’s on good, if not it’s the other one.
Now if the basement is in ADDITION to the three floors, I get out my trusty voltmeter that I always carry around with me and probe it.
That was the way I worked it out, as well.
I’m with Max on this one – I’d have been either leaning out the basement window or using a mirror to see up to the 2nd floor. Or I’d have MacGyver tear apart the wiring to figure out which switch goes to what light fixture on what floor.
My daughter says your daughter told you the right answer.
As I turn the switches off and on I look out the tiny basement windows and make a decision?
This coming from a wife whose husband is traveling quite a bit.
I’m usually right…
I had the same thought oldskydog did–assumed one switch was for the 1st floor.
Turn on each switch individually, going to the first floor after each switch is tested until the 1st floor light is on.
Turn on either of the other switches and proceed to the second floor. If the 2nd floor light is on, the switch you turned on is the correct switch. If not, the other switch is the one for the 2nd floor.
If any of the lights are burned out, you may be screwed.
Max/
Which way is the liquor cabinet again?
Correct me if I’m wrong. I saw no constraint against turning on all three switches while in the basement. Bound to get the second floor that way. Although, the greenies moght have a fit.
Why the heck are all the light switches in the basement??
You people have way too much time on your hands…
I really like your readers… and I’m for drinking in the dark!
I’d just send my kid up to the second floor, then throw the switches one at a time until she hollers down that the light is on. Then I’d mark it with a grease pencil. I’d also have her pull me a beer from the ready rack in the fridge on the way back down.
Kids can be very useful after a certain age
And before another age. The range between the two varies, but in all cases is WAY too short.
Easy. Flip each switch on and off rapidly, and when someone yells at you to knock it off, ask them which floor they are on.
Car Talk with Click & Clack the Tappit Brothers had this teaser on as one of their “Puzzlers” two or three years ago…alas I didn’t get it then… and unfortunately I didn’t remember the answer this time. Best
I don’t know where the liquor cabinet is, but aside from the wine cellar the basement’s finished, so why leave?
This is the funniest thread I’ve read in a long time – made all the more hilarious by the unique collection of characters who congregate in these environs.
Which is to say you’re all a bunch of wackos.
Myself included.
Oh, my solution was to drill a hole in the bulb on the second floor, put some black powder in it flip the switches one by one. When the smoke detector goes off you know you’ve found the right one.
Oh, on your one trip to the second floor you might want to bring a fire extinguisher with you.