Brain Quiz #6

Three switches outside a windowless room are connected to three lightbulbs inside the room. How can you determine which switch is connected to each bulb if you may enter the room only once?

Difficulty Rating: 10

15 thoughts on “Brain Quiz #6

  1. flip first switch on, wait for a while, and then turn it off. flip second switch on and enter room. immediately check to see which of the two “off” light bulbs is hot to the touch–this one matches the first switch. the “on” light bulb matches the second switch and the cool “off” light bulb matches the third switch.

  2. I’ve heard this one before, but it took me a while to remember:
    Turn on switch 1, then wait five minutes, turn it off, and turn on switch 2. Go into the room immediately, and you’ll be able to tell that the warm bulb is #1, the lit one is 2, and the other is 3.

  3. I’ll say it again to help you out here: You must enter the room in order to see the lights. You can’t just be leaving the door open and see them from outside.

  4. turn on the first switch wait a while turn it off then turn on the second one and go into the other room and which ever one is hot to touch is the first one the light on is the second one and the other goes with the other

  5. First you flip one switch leave it on for a while the turn it off. Next you flip on the second switch and go in the room. The light bulb that’s warm and off is the first switch. The light bulb that’s off and not warm is the third switch and we are left to believe the second switch goes to the light that is on.

  6. Turn on switches A and B and leave them running for a few minutes. Turn off switch B.

    The bulb for switch A is lit. The bulb for switch B is unlit, but hot. The bulb for switch C is unlit and cool.

    (My dad’s a smarty pants jerk.)

  7. (My wrong answers)

    Enter the room and reach outside to tweak the switches while you watch the bulbs from inside the room. Use a long stick, if necessary, to reach the switches.

    Alternatively, get a friend to tweak the switches.

    Alternatively, enter the room and disassemble the light fixtures, leaving bare wires. Exit the room, remove the switch casings, and pull the wires through one by one.

  8. Can you unplug one light bulb, turn one on and leave the third off? This of course would necessitate that you walk in the room before the experiment.

  9. Turn on two of the lights and leave them on for a little while. Turn off one of those lights and walk into the room. There will be a cold lightbulb, a warm one and one that is still on…

    As long as you remember which switch you turned back off, you will know which switch belongs to which bulb.

  10. Turn on two switches. Before entering the room, turn one off. The light that is on is connected to the swtich left on. The light bulb that is off and hot is connected to the switch that was turned off just before entering. The bulb that is off and cold is the remaining switch.

  11. Switch the first light on, wait for a minute, then switch it off. then switch on the second light, and enter the room. The recently turned off light will still be warm, the second one will be on, and the third will be off and cold.

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