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You'd get walkouts? Any person with normal intelligence and average facility with math realizes within 3 minutes that (2*3)-5 = 1.

People who have trouble with that problem have no guts.

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This requires realizing that you can stop pouring. It isn't as in your face obvious as you're making it out to be.

The solution became immediately obvious to me after reading your comment. This leads me to believe that the question isn’t testing for math ability nor intelligence. It just requires you to realize the trick. Maybe it tests for creativity / lateral thinking ability?

It is not a trick so much as thinking what kinds of operations can be done with these vessels and water. Not necessarily a good interview question, but may be a good discussion with a young student.

random1538 didn't say what kind of engineers they were hiring, but if it was software engineers I'd be confused by it too. I know the solution to the problem, but only because I've seen it before and thus know the method to solve it.

If they were hiring cooks / chemists / anyone that is expected to have experience with measuring liquid volumes, it might make sense to assume they have the experience needed to solve this problem.

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