I have done B.A. with mathematics can I choose mathematics in B.Ed?

Hello, Yes, you can. Graduation subject has nothing to do with B.Ed subject. All the B.Ed colleges follow the syllabus prescribed by the NCTE. Though the name of books and authors may differ, all the colleges teach theory papers that deal with Educational Philosophy, Educational Psychology, School A

Yes, you can choose mathematics in B.Ed. After you get admission in B.Ed college you have to choose one teaching subject, so then you can choose mathematics as your teaching subject.