What the pattern is this year, how the marking really works, and how to plan the year. Facts from the bulletins and the papers; nothing goes out before a second person has read it.
Very nearly for Biology, mostly for Chemistry, and for Physics the book gives the ideas while the exam asks for speed. What 'enough' means, subject by subject.
The honest answer is a range, and the number matters less than three other things: what the hours contain, whether they repeat, and when the questions start.
Physics and Chemistry are shared; Biology and Mathematics are not, and they decide each exam. What the overlap costs, and how to decide by the end of Class 11.