How do I study to get 80% in cbse board exams starting from today?

I assume that you are from science stream.
I also started in the first week of February and also had about 40% knowledge of my syllabus and i knew i was screwed up beacuse all my friends were busy revising 2 or 3rd time .
But then i decided not to waste my life and brought book called EXAM IDEA for each subject (as recommended by my teacher)and from then i used to study all day .
I finished my maths in almost 10 days and then i started chemistry which took about a week and then i was left with few days 3-4 days i studied physics book 1 as i knew i had 7 days gap in my physics,5 in maths and 2 in chem . I studies smart not hard( obvious i did not had enough time)
In between exams in first 2 days i used to do chapters i didn’t knew at all.
I never lost my hope and i was aiming above 90%.
Which according to my teachers was impossible.
I scored 94.8% in cbse boards and also cleared jeemains (108).
So good luck and start studying its never too late. 🙂