Dear Mr. Anand,
There is not a hard and fast rule to get admission in IIT. this things depend on the quality , difficulty, student standard and cut off of that particular year. But for selection point , you will have to score minimum 25% of total marks.
Please feel free to post as many doubts on our discussion forum as you can.
If you find any question Difficult to understand - post it here and we will get you the answer and detailed
solution very quickly.
We are all IITians and here to help you in your IIT JEE & AIEEE preparation.
All the best.