the eligibility criteria for apply for Indian army is candidate must have passed their 10+2 from recognized board and the candidate appearing for 12th are also eligible but to apply for Indian navy and AIR force you must have passed your 10+2 from recognized board with physics and mathematics as compulsory subject.
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The age limit to appear in NDA is 16.5 years to 19.5 years. If your age is below 19.5 years then you can apply NDA if not you are not eligible. Candidates must have passed 10+2 with Mathematics, Physics and Chemistry to join AFA and INA. Candidates must have passed 10+2 with any stream from a recognized board to join IMA.