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!
Well...
case 1: I know beforehand that this is going to be an interview to look at how good I am at reasoning. No problem, give me the question about bus to fill with balls
case 2: this is going to be a more informal interview, question goes in the same list as "your name, what were you doing at your previous job, did you work with X... by the way, what about switches and bulbs" - nope. That means interviewer did a lousy job at preparing for interview, so who is wasting whose time - up to me to decide on the spot