Dear aspirant !

Hope you are doing great ! Don't think about number of attempts , only 1 attempt is required to clear any exam .

Firstly focus on class 11 ,start preparing from class 11 for nda in following way ;-

Preparation Tips

1. Revision of Class 10th, 11th, and 12th Mathematics.
2. Maintain a separate sheet for the formulas and short tricks for calculation.
3. Practice the UPSC NDA Previous year papers and try to attempt the questions.
4. Attempt Sample papers and test series regularly to get accurate and precise answers..

However ,you will get 4 to 5 attempt which I think are enough to clear the exam .

For more about nda ,visit the link ;-

https://www.google.com/url?sa=t&source=web&rct=j&url=https://competition.careers360.com/exams/nda/amp&ved=2ahUKEwjR8eOjoJ74AhUI4DgGHcliDm0QFnoECAYQAQ&usg=AOvVaw2rE--RRTEeWDolGBpNFhOj ..

Hope it helps you !!

Thanking you