This question was made famous when Microsoft began using it in job interviews. It is an example of a creative problem-solving question that is used to assess how a person approaches a problem with more than one possible answer, and to test their logic, common sense and ability to think through an unusual question in a high-pressure interview setting.
According to Joel Spolsky, one of Microsoft’s early program managers, questions like these distinguish between people who are smart and get things done, people who are smart but don’t get things done, and people who get things done but are not smart.
Microsoft must have been onto something, because this type of question has been adopted by many other companies as an alternative to more traditional interview questions.
A number of possible explanations for why manhole covers are round include: