You Are In A Room With Three Light Switches

The three switches control three light bulbs in another room. You are allowed one (and only one) trip to the other room, at which time you have to determine which switch controls which bulb.

Punishment for failure to solve this, is having to listen to Obama speak for an hour.

This is a simple problem, but if you think like a computer geek you will never solve it.

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65 Responses to You Are In A Room With Three Light Switches

  1. inMAGICn says:

    An oldie but goodie.

    Good luck and good thinking.

    • Toppleton Geardom says:

      Get a light socket outlet adapter (such as the Leviton 1403-I) an extension cord, and a fan (or other handy appliance.) Unscrew the bulb in the room you are testing, insert the light socket adapter, plug in the extension cord, unwind it as you walk back to the room with the switches, and then test which switch turns on your fan.

  2. inMAGICn says:

    ….and don’t Google it!

  3. Jack Clancy says:

    I don’t know but somebody solve this soon I’m going to be with some demoncrats tonight and I want to use this.

  4. hifast says:

    Turn on switch A for five minutes and then turn it off. Turn on switch B. Go to the room. The dark warm bulb is A, the lit one is B, and the cold dark one is C.

    • philjourdan says:

      But they are the new CFL bulbs. They never get warm. They never get cold. They never burn out. They are not an environmental hazard. they are not…..

      Wait, what were we talking about?

    • _Jim says:

      I vote for your answer, for a single-person solution.

      Change the procedure though to run one bulb for a full ten minutes BUT 8 min into that run fire up only one other bulb for the balance of the ten minutes … check the temps of the bulbs on the other end.

    • John B., M.D. says:

      Good job hifast! I didn’t think of that.

    • Tom Bakert says:

      That was my solution, too. BTW, I am a retired software geek. Computers were just the tools I used.

  5. _Jim says:

    Simple … phone a friend (or, a bellhop) into the room with the switches while you go visit the room with the light bulbs while the friend or bellhop works the switches one by one …

  6. Bob F says:

    With my experience of CFL bulbs you wouldn’t be able to tell which one was still on when you went into the room

  7. Sophie says:

    The line, ‘The three switches control three light bulbs in another room’ The way it reads, that could mean the three switches as well as the lightbulbs are in the other room?

  8. mjc says:

    Apply for a grant to study the problem.

    • jeo says:

      But first determine what the grant-maker wants to learn from the study, then apply for the grant, then tell the grant-maker what he wanted to hear in the first place.

  9. Eric Baker says:

    The first switch controls the second light, the second switch controls the first light and the third switch controls the third light. Anyone who disagrees is anti-science…and no, I will not tell you my methodology. Glad that’s settled.

    • Andy Oz says:

      The lights are melting fast and will be all gone by August.
      There is also a polar bear in the room who is gonna be pissed when it goes dark.
      Give me a government grant and I’ll solve the problem.

    • philjourdan says:

      The Climate science method! Very good!

    • Jason Calley says:


      Actually, it does not matter which switch controls which bulb. Any CO2 over 350 ppm will make all the bulbs burn out anyway.

  10. John Silver says:

    I just follow the wire.

  11. baconman says:

    For CFL’s turn 2 on for 5 minutes, then turn one of those two off and immediately go to the room. The one that is still flickering and giving you a seizure is the one you just turned off.

  12. Ernie says:

    Dimmer switches at different levels.

  13. Mike D says:

    Check this story out, and this quote from it:

    “But one Russian expert says the cause is more likely to be global warming releasing gases under the surface, which then explode like a champagne cork.”

  14. Hugh K says:

    Offer 100 million dollars to the Democrat party and they will say anything you want to hear.

  15. tom0mason says:

    It is not resolvable as TOB data has been adjusted.

  16. Morgan says:

    Take a trip to the other room and leave the door open when you come back. No problem.

  17. Buzzy243 says:

    Easy. Have Obama turn on the switches, one at a time, while you watch to see which bulbs light up in the other room.

  18. stewart pid says:

    Excuse me teacher can we adjust for the time of observation of the bulb and can we model the problem on a SUPER COMPUTER?

  19. As Hillary would say “what difference does it make” you only need one light to see in that other room so any switch will work, just grab the other 2 light bulbs send them to congress.

  20. Edmonton Al says:

    You are in the room with the bulbs. Say 3 bulbs on.
    Unscrew one bulb; go into the room with the switches and reverse 2 switches.
    go back to room wth bulbs and see the changes.
    Keep track of which bulbs change [or not]

  21. Matt L. says:

    “Turn on switch A for five minutes and then turn it off. Turn on switch B. Go to the room. The dark warm bulb is A, the lit one is B, and the cold dark one is C. -hifast”


    First step is to write a science-y paper opining exactly why your arbitrary choice is infallibly correct. Next, have your peers review your paper and build a strong consensus. Finally, flip all the switches, walk into the room and forcefully declare that both light and the absence of light are killing redheads, raising oceans and shrinking underpants.

  22. David A says:

    “Punishment for failure to solve this, is having to listen to Obama speak for an hour.”

    Which is the answer to the question of how to turn off 300 million lights at once.

  23. drtim12 says:

    Harry Reid’s finger in one socket,Hillary”s in the other 2 and It doesn’t make a difference just turn them all on at once and enjoy the music.

  24. Edmonton Al says:

    Leave the door open and place a mirror in the room.
    Flick the switches and make note.

  25. Bob Greene says:

    I believe the punishment is banned by the Geneva and Hague conventions as cruel and unusual. I’d try the solution if the punishment was a meal of MRE chicken a la king and MRE dessicated (desecrated) pork patty, which are lower on the cruel and unusual punishment scale.

  26. Sparks says:

    It’s a movie reference ffs… I feel your pain dude.

  27. powderslider says:

    I don’t need a trip to the other room, “The three switches control three light bulbs in another room”, it does not say each switch controls only one light bulb. BOOM!

  28. Sparks says:

    Here is how to solve it, self destruct!

  29. squid2112 says:

    Brain Games is a pretty good show. I record and watch every episode. They have some pretty interesting things sometimes.

  30. send someone else into the room + ask them to let you know which light comes on when you flip the switch 🙂 it is good to have friends

  31. Eric Simpson says:

    Punishment for failure to solve this, is having to listen to Obama speak for an hour.
    Nope. I’m bailing. I’m out of the house and headed for the hills!

  32. Scott says:

    But two of the bulbs and switches MAY be on a 3-way circuit, or may not be. Good luck with that. Oh, and 0-3 of the bulbs may be burnt out…looks like homogenization is the only answer because it gives a negative UHI effect.


  33. edward1968 says:

    Am I required to stay awake for the entire hour? I could use a nap.

  34. Ric Werme says:

    I first heard this on Car Talk , a US radio show that sometimes talk about cars. It was presented a week after Tom and Ray made a comment that Martin Gardner had died some time ago. He was the long time author of Mathematical Games back when Scientific American was worth saving. Gardner’s son called the next week to assure everyone that Gardner was still alive, at least that morning, and passed on this puzzle, with the variant that the switches controlled lights two floors up and you don’t like climbing stairs.

    That was several years ago, and Gardner has since died. He’s been missed and celebrated, and it it weren’t for him, I wouldn’t know about Soma Cubes, hexaflexagons, Dr. Matrix and all sorts of stuff that made Mathematical Games so great.

  35. Sophie says:

    Mm, I do wonder how many alarmists it would take to change a light bulb?
    One to change it and 97% to say the new light bulb is a lot warmer than the old one – which continues to cool – making the trend looks unprecedented!

    P.S. The old light bulb was original fitted in the 1930’s

    • Andy Oz says:

      I have checked some random tree rings and the light bulb was much much cooler in the 1930’s than now.

  36. Sophie says:

    Ah, does that not depend on the climate sensitivity? If you are checking the tree ring data with a manometer, I believe it is a little bit too sensitive. 

  37. Edmonton Al says:

    Doug Rogalla (@RealCheezed) says: …………………….
    I like your answer. Is it permitted??

  38. Dougmanxx says:

    The answer to this is so simple, I’m amazed no one has come up with this:

    1. Leave the building and go for a drive in your car.
    2. Find the nearest “toxic waste disposal area”.
    3. Follow the “toxic waste disposal trucks” as much as you possibly can, while attempting to get into an “accident” which covers you in “toxic sludge”.
    4. Once you have achieved your goal of “accidentally” being doused in “toxic sludge”, return to the building with the rooms.
    5. Use the resultant superpowers from your “toxic accident” to peer through the wall and see which light bulb lights with which switch.

    See? Piece of cake! This would work for the original as well, assuming the room you were in to start was on the first floor. Of course with your new found superpowers you could simply fly, ignoring the stairs completely!

  39. Buy a duck. Have the duck figure it out for you.

  40. bob droege says:

    Find the owner of the building and give him the brand new manometer if he will tell you which switch operates which bulb.

  41. John Q. Galt says:

    You are in a room with Neil deGrasse Tyson and he is doing his little Rubik’s Cube trick.
    You are an Engineer and have your own Rubik’s Cube.

    How do you solve the problem in a way that pisses off the audience of 20-something libtard college students sitting in the corner of the room fawning over Tyson?

  42. John Q. Galt says:

    Mysteries of the Cosmos.

    Actual Time Warner Cable channel line-up:

    Channel 43 ESPNHD
    Channel 44 MSNBCHD
    Channel 45 TOONHD

    Question: How are these things the same and how are these things different?

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