[arupchak]

I've always found that asking a reasonable numerical solving question where you can easily figure out the answer in your head is a good starting point to gauge programming/algorithm ability. If someone knows the solution they are trying to get at, they can focus on the program itself, as opposed to worrying about solving the problem and coming up with the algorithm. Ideally there are a few ways to solve the problem, brute-force methods or more efficient ways. It can be very difficult to test a programmer's ability in an interview, you need to focus more on seeing how the candidate thinks, how they approach problems, and whether they can admit when they do not know something.