Hello

For admissions to NITs / IIITs / GFTIs :

• Candidates need to have secured a minimum 75% marks in class XII or equivalent exam or be in the top 20 percentile in their class XII exam conducted by the respective board.
• For SC/ ST candidates, the eligibility criteria is to secure 65% marks in class XII or equivalent exam.

For admissions to B.Arch. programmes:

• Candidates need to have PCM mandatorily in their 10+2 or equivalent exam.
• They need to have secured minimum 50% marks in these subjects in aggregate and 50% individually too.

Good luck I hope this helps you

In order to take admission in IITs, NITs, IIITs you should have the aggregate score of Physics, Chemistry and Mathematics 75% in class 12th as per the eligibility. You can check the further eligibility of JEE Main & JEE Advance with the given below links.

JEE Main Eligibility

JEE Advance Eligibility

Good Luck!

yes it is necssary because rank and college choice filling  is based on the average marks of your academics percentile and jee mains marks