Simply add two parts Mathematics, one part Physics, and one part Chemistry to get a total of 200.
For example, if you received 90 points in Mathematics, Physics, and Chemistry, your cut-off is 90/100 (Math) + 45/50 (Physics) + 45/50 (Chemistry) = 180/200. And you must compete with students from all other states, except Tamil Nadu, against their marks calculated in this manner, regardless of whether they are CBSE or not.