On interviews, I like to ask a couple questions from Programming Pearls. I know it's old, but I love that book. For estimation, "how many gallons a day flow ou

On interviews, I like to ask a couple questions from Programming Pearls. I know it's old, but I love that book. For estimation, "how many gallons a day flow out of the Mississippi River?" Most people say "I don't know" and won't even try to answer. But when you see someone come up with an estimate and rationalize it, that's a good sign. I don't know what I'd do now if someone actually went to Wolfram Alpha, Wikipedia, etc. and looked it up. I like to see coders answer things like: you're building a 40' fence with 5' fence sections. How many fence posts are there? It seems trivial, but I'm amazed how many people get it wrong at first ("8. No, wait, 9. Yeah, 9.") and really amazed by how many never realize that 8 is wrong.