My elder brother completed his education at IIM Indore. So I think I can answer your question.

IIM Indore provides an IPM (Integrated Program in Management) course after you complete your high school education. It's a five-year program that has proven to be really beneficial. In those five years, you'll have acquired comprehensive management skills. Math is required in this course. So, students coming from a Math background do have an advantage. But there are students with non-mathematical backgrounds too. So, you can definitely have a seat at IIM Indore, even if you didn’t have maths in 12th. 

But don't be discouraged, the MBA and PGDM programs do not require math in class 12; all you need to do is pass the CAT exam. You'll need to study hard for that, as it's a competitive and difficult exam. So plan beforehand and give it your all. IIM Indore is an amazing institute, and it is well worth your time to study there.