Hi Saksham,

You are eligible to apply for M.A. Economics in all these reputed institutions. This is because many Maths people switch to Economics at the postgraduate level due to more Interest/scope in that line. Economics is pretty much linked with Mathematics. However, you need to prepare well for the entrances as you'd be at a weaker spot due to non-economics background. Remain updated with the syllabus and prepare accordingly by much practice.

All the best!