Hello,

For such calculations, you need to learn specific values. Usually uncommon calculations do not come. There are some common values surrounding which the questions are given. Go through the previous year questions and you'll be able to identify them easily. As for the calculations, if such uncommon values are given, you have to calculate them consuming time. Do not worry, since the question paper is set very wisely in the time allotment field and tough calculations are tough for everyone. Just keep the sums having such calculations for last. To make your calculations fast, practice is the only way.