Hello,

Yes, you are eligible to appear for NDA but you can join only Indian Military Academy if you qualify in NDA and SSB interview. Candidates who have passed 10+2 with Mathematics and Physics from a recognized board are eligible to join Indian Air Force Academy, Indian Naval Academy and Indian Military Academy. Candidates who have passed 10+2 in any stream are eligible to join Indian Military Academy. The age limit is 16.5 years to 19.5 years.

Yes, you can give NDA exam with pcb and join army. But it will be very difficult for you to clear the exam as you are a non-maths student and there is a compulsory paper of mathematics in the NDA entrance exam in which question of 12th level of mathematics are asked. Visit past year papers of NDA here -http://www.upsc.gov.in/examinations/question-papers. If you want to join defence after graduation, you can give CDS and AFCAT exams.