Hi,

The eligibility for UPSC Civil Services is to just have graduation in any stream. Your hold in Mathematics is not a problem at all. The syllabus for UPSC exam usually consists of syllabus from Arts stream. It would be a bonus point if you are good at Arts. So, do not worry, just check out the syllabus and opt for optional subject wisely which can help you out in the preparation. You can even opt for graduation in Arts stream. Check all the syllabus and other details  for UPSC Civil Services over here: https://competition.careers360.com/exams/upsc-civil-services-exam