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!
Thr difference in phrasing is that your question presents a reasonable objective rather than an unreasonable constraint. You're also asking something subject-specific from someone who ought to be versed in that subject. That's not a riddle, it's a task you're expecting your hire to be capable of.
That's kind of my point. Google started that nonsense of making job interviews into lateral thinking puzzles, then all managers latched onto that to make themselves look hip.
I want to see competence and practical problem solving skills.