Just go through all the logics for prilims these 2 sections are scoring - 10 marks
practice with strategy....go to YouTube and search for tricks so that you'll be able to solve ques in less time...practice is not the only strategy...
Practice Practice & Practice!!! And yeah you should have good command over Basic Calculation. You should remember tables upto 20. Squares upto 32. Cubes upto 20.
Prefer the book Quicker maths by M. Tyra