Want to go for additional papers for mathematics

You are doing your B.Ed. The subjects you opted for or Mathematics and Economics. Once you complete this course you will become teacher. You can be posted as mathematics teacher or social Science teacher. That depends on for which subject you will write DSC examination and you will get selected. You need not go for any additional papers in mathematics. For your interest you can appear for additional BA degree with mathematics. But this is not required for your teaching post. Whatever may be your subjects on BA, your B Ed subjects are important for teacher post.

You better go for PG course in Social Sciences or Mathematics. Once you complete that course you can try for a lecturer post or even you can go for PhD.

Generally while taking admission in B.Ed. one has to choose the subjects from the given categories and you might have seen that at the time of admission. The subjects taken should be different in the sense that they should be chosen from the two different baskets as per the curriculum of the B.Ed. in that particular institution. There are many subjects which you might had not read in your graduation. As far as possible one has to stick to ones own subject of graduation but it is not mandatory and if you have proficiency in any of the subjects you can choose it. Even one can choose a major and minor same language.

What I will suggest that you should learn and acquire proficiency in the Mathematics so that you can teach it to the students without any problem. You can even go for online correspondence course in B.A. Mathematics from any institution to increase your knowledge in Mathematics.

The subjects chosen at the B.Ed stage need not necessarily be the same as that of graduation stage. Normally candidates prefer to opt the subjects with which they have acquired their graduation degree. However, the same may not be mandatory and the selection of the subjects at B.Ed stage would also depend upon the candidate's interest and passion.
So while including Mathematics as one of papers at B.Ed stage, you should be familiar with the cirriculam of Mathematics taught at the graduation - level and see to what extent, you are comfortable in grasping this subject. You can even go online correspondance course in Mathematics dealing with Algebra, Trigonometry, Differential and Integral calculus, Differential - equation, Vector - algebra etc so that while teaching Mathematics at the school - level, you are not loosing your confidence.
The option lies in taking up a post - graduation degree either in Social - science or Mathematics depending upon your interest after completing your B.Ed course. At the later stage, you can write NET so that you may be inducted for the post of lecturer in a constituent college after going through the selection procedure of NET.

As already you are doing B.Ed with subjects combination of Economics and Maths and the course is about to completed soon. To teach mathematics you should have mathematics at graduation level. You will be able to teach all subjects to primary classes. But I think you will not be eligible to teach Maths in junior classes as you have not taken mathematics subject in graduation level. If you are planning to take addition paper of mathematics, it may be beneficial for you. Otherwise you will be eligible to teach social science.

In many States there are two streams in B.Ed i.e. Maths and Science and social science. You will have to qualify CTET in the respective stream. If you are having science subjects like science and Maths you are eligible to teach science and Maths subjects. If you have done graduation in Arts subjects then you are eligible to teach social science subjects. Any student who has taken mathematics as main subject can choose Maths in B.Ed. You have not written that in which stream you had studied. You should not have chosen mathematics while you had not studied it at graduation level. But now the situation is that your B.Ed is about to complete, there are two options available, you can go with:
1. You can take Mathematics as additional paper and give separate exam.
2. You can do PG in mathematics

But I think you should qualify CTET in Social Sciences and apply for social science subject upto 10th classes. After completing PG either in economics or mathematics you will be eligible to apply for teaching upto 12th classes. But
I am not sure that without studying Mathematics at graduate level whether you are eligible to do PG in Mathematics.
Further, you can qualify NET exam and do Ph.D. also and you will be eligible to teach degree classes.