Hey!

The answer to your question isn't that simple. One only gets a hundred percentile when nobody scored more than them. So you need to score the most marks in physics and the other two subjects as well, the marks aren't fixed but you can imagine how much you need to have 100 percentile. Try to score above 270. Also, either physics or mathematics is most important while scoring depending on which paper was the first one in the question paper so focus more om physics and mathematics but don't leave chemistry completely as it can lower your percentile.