Hello Ajay,

If you want to answer 20 questions from overall paper, focus more on the topics from which sure shot and more number of questions are likely to appear. From physics, focus more on motion in a straight line, motion in a plane, electrical circuits. From chemistry, focus more on organic chemistry and p,d,f block elements. From maths, focus more on vectors, straight lines, coordinate geometry and calculus. Also, see that you go through small small chapters so that you don't miss out scores.