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.
Comment:
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!
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.This assumes several things to be true, which might not be true:
If any of the above is not true, the conclusion is invalid.
Also that the labels are as shown. For all we know the internal wiring is switched, and if that were the case then some could have Up=On while others have Up=Off but not all matching.
Also:
I'll go one further:
The biggest flaw is that it assumes you’ll add conditions you’re not explicitly told are allowed. Many, many problems in school would be trivial if changing the terms beyond what’s stated was allowed.
This is often exactly what the interview question is testing. Many of these questions are not about the solution but about how the applicant approaches problems
Also the image shows all 3 switches are on.
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
If I asked this question during an interview and the candidate gave me this list of assumptions, I would recommend the candidate. This is exactly what I would be looking for by asking a vague question, not if they memorized the answer to a bunch of riddles, but how they thought and what their line of thought was for troubleshooting the answer.
I tend to agree with this line of thinking. If you're trying to hire an effective problem solver, well the first step to solving any problem is understanding the problem - the whole problem - and often more importantly the context in which the problem exists.
And while my first reaction is to be frustrated with the person asking for a solution to such a vague problem... in the real world problems are rarely clearly stated, and frequently misstated. Investigating the apparent conditions of the problem is always necessary, and generally the fastest path to resolution.
You'd be boned if it's an LED bulb that doesn't warm up noticeably.
This riddle has been around for so long it predates LEDs and pedantic software engineers.
Or if it was turned on to begin with and you just turned it off
Text ambiguous. Leave doors(s) between rooms open. Flip switches, see which one controls bulb in other room. No need to even visit other room. Done in seconds.
This also assumes youre alone, a practical person would send someone else in the other room and communicate the states back
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Nice try, they recently upgraded to led lights.Assumes that the bulb can be touched, that it is hot when turned on, and that the position of the switch for 'on' is the standard position.