Hello aspirant,

This itself is a very difficult question since the highest percentile, i.e. 100, keeps varying each year. For instance, if the highest marks obtained by a student in JEE Mains is 250 out of 300, then 250 becomes the 100 percentile and all other marks and percentiles are tallied accordingly. Moreover, the percentile also depends upon a number of other factors such as the difficulty level of exam. the no of aspirants, the no of shifts in which the exam was conducted, etc.

So in order to score the highest marks, you need to be able to answer the most number of questions in a given amount of time, without second guessing. Since that leads to negative marking.

For more details regarding the syllabus, visit the link below:
https://engineering.careers360.com/articles/jee-main-syllabus

Hope this helps you.