this post was submitted on 25 Dec 2025
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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!

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[–] partial_accumen@lemmy.world 148 points 2 days ago (2 children)

I'll go one further:

  • Assumes the bulb is in reach. When I read the problem I assumed the bulb was in a ceiling fixture out of reach. Nowhere in the text description did it specify the physical location, except "in the other room".
[–] TeamAssimilation@infosec.pub 46 points 2 days ago (1 children)

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.

[–] neatchee@piefed.social 7 points 2 days ago (1 children)

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

[–] TeamAssimilation@infosec.pub 3 points 1 day ago* (last edited 1 day ago) (1 children)

Yet they never explicitly state you’re allowed to make convenient assumptions. If the bulb was out of hand’s reach the problem would be unsolvable.

Assuming the electrician that wired the switches is in the room would be even a more out-of-the-box solution.

[–] neatchee@piefed.social 1 points 1 day ago

As I said, they care about how you think. Do you ask all these questions?

if I were given this interview question I would immediately start asking questions: Do I have my phone? Can I bring any objects into the room? Do I know the construction of the light? How far from the room is the light switch panel?

Asking "what are the limitations and conditions of this situation" is literally the thing they want to see. That's my entire point.

[–] db2@lemmy.world 21 points 2 days ago

Also the image shows all 3 switches are on.