Hello Kanchan! firstly, let me tell you that BA LLB is provided by numerous universities/ colleges. Therefore, the entrance exam for BA LLB are in abundance. 

I can just tell you the basic topics that are covered in the syllabus of every exam. But to get an in depth knowledge i would recommend you to check the syllabus of the exam you are willing to give.

SYLLABUS

• English including comprehension.
• General knowledge and current affairs
• Elementary mathematics/ Numerical ability/ Mental ability
• Legal Aptitude
• Logical Reasoning

ENTRANCE EXAMS

• All India Law Entrance Test (AILET)
• Common Law Admission Test (CLAT)
• Law School Admission Test for India (LSAT India)
• Army Institue of Law Entrance Test  (AIL LET)
• Banaras Hindu University Undergraduate Entrance Test (BHU UET)

These are some of the entrance examinations.

SCOPE

Even if you are a maths student and willing to pursue law, there is no harm in doing so.

Maths actually helps an individual in every entrance exam ( because of the mental ability test incorporated in these competitive exams).

AFTER BA LLB

Various opportunities open up for you:

• Special Officer Law (for bank)
• Judge Advocate General (JAG) (for military)
• Assistant District Prosecution Officer (ADPO)
• Working as an Advocate for MNC
• Examination for Judicial Services etc.

At the end i would say that, if you are willing to do BA LLB then its a very good thing. It will be helpful in cracking UPSC as well. And later in life, if you develop an interest towards law, you can practice as an advocate anytime.

All the Best!

I hope this helps.