How to increase the speed in number system problem

1) There are quite a few formulae and concepts in Number System. Knowing the concepts beforehand will help you to get to the trick immediately after reading the question. This saves a lot of time which can be used better elsewhere.
2) A lot of practice is required. Practice all types of problems, but concentrate more on remainders, HCF-LCM and base system as questions from these topics can be quite tricky.
3) Don't depend a lot on the given calculator as it takes a lot of time in clicking each button. Improving your calculation speed will significantly help to reduce the amount of time you spend on a question.