NDA

NDA doesn't accept B.Tech graduates. It is for class 12th pass or appearing students.

Hi, yes you are eligibile for NDA and all government job exams after 12th from NIOS.

Hello Ritesh,
Firstly, try to find where have you left portions in your preparation or which part is weak.
Make a list of all weak chapters and then study smartly.
Never think while studying that I already studied this chapter in previous year.
Never leave maths as many students think that it is too hard to do.
Don't waste time in joining coaching just purchase the package by coaching institute and then go for it.

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There, you can know more about NDA Application details.

As I think for maths part of NDA, you have to prepare like JEE main maths with time management and also, practice more and more previous year question papers for getting more ideas. If you liked my answer, please upvote.

There is a strict age limit which is 16.5 years to 19.5 years that you should follow. Further, you must join a good coaching centre for preparation if you are desperate to join NDA.

Science is required only if you aim for Air-force or Navy and else, arts graduate can also participate.