1. Because computer science is about mathematics (combinatorics, permutations, counting, etc) and sometimes interviewers want to make sure that the candidate's

1. Because computer science is about mathematics (combinatorics, permutations, counting, etc) and sometimes interviewers want to make sure that the candidate's foundation is solid. 2. As stated in earlier comments, because mathematics is unambiguous making the problem easy to state and easy to verify. Can you take a small piece of mathematics you may not be familiar with, understand it and translate that into working code? That is a core skill of any software developer -- not necessarily with just mathematics but you get the point.