Post:

You have three switches in one room and a single light bulb in another room. You are allowed to visit the room with the light bulb only once. How do you figure out which switch controls the bulb? Write your answer in the comments before looking at other answers.

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If this were an interview question, the correct response would be "Do you have any relevant questions for me? Because have a long list of things that more deserving of my precious time than to think about this!

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[–] otacon239@lemmy.world 187 points 1 day ago (19 children)

For those that want the actual answer:

Tap for spoiler

You turn on the first switch for a minute or two, turn it off, and turn on the second switch. If the bulb is on, it’s obviously the second switch. If the bulb is off and warm, it’s the first switch. If it’s cold, it’s the third switch.

[–] NaibofTabr@infosec.pub 230 points 1 day ago (10 children)

This assumes several things to be true, which might not be true:

power is available/the upstream circuit is on (always a bad assumption to make)
the bulb is an incandescent type that will generate an appreciable amount of heat in a short amount of time
the bulb was in the off state before you changed the position of any switches, and has been off long enough to be cold
the bulb is connected to any of the switches
the bulb is connected to only one of the switches (parallel circuits are a thing, as are multi-switch lighting circuits)

If any of the above is not true, the conclusion is invalid.

[–] taiyang@lemmy.world 13 points 22 hours ago

I love the idea of someone trying this stupid question irl only to realize it wasn't even plugged in. That's ... well fuck, that's most IT work. The convoluted approach is definitely the wrong one. Lol

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