Why do you think manholes are round in shape?
(You need to think a little crooked for this )
(In reply to
re: A solution by levik)
Yes, this is quite a popular interview question. However, at least when I've been asked it, it usually gets phrased as "give 5 reasons why..." which is pretty stupid as there aren't 5 reasons why, so you end up coming up with lame responses for the end couple. Ah well.