Hi,

The ability to remember and recall  is different for each individual. So what percentage one get depends on the individual. Because some take 3-4 hours to understand a topic and some understand in just minutes.

Navneet 21 sets are good for preparing HSC exam. They really help a student. If you prepare from the Navneet 21 books you can get minimum 60-65% marks easily. However I would suggest you that you should also study the text book. Because they ata the main source of information in HSC exam.

Hope you find this helpful. All the best for your exams.