Faster calculations in Quants

Estimation Some problems ask you straight up, “Approximately how far has the train gone when…” When they tell you that you can approximate, always do so! But even when they don’t, you may be able to estimate. Train yourself to glance at those answer choices periodically while you work to see how far you really need to go. The correct answer isn’t the actual number,the correct answer is just A, B, C, or D. Who cares how you get there? In general, if you have numerical answer choices that are decently far apart, you can often estimate at some point in the problem—possibly right from the beginning or possibly a little farther in, depending upon the nature of the problem and how far apart the answers are. Also, how rough can your estimation be? Again, glance at those answers. The farther apart they are, the more loose you can be. You’ll need to practice this, like any skill, so that you know how far is too far. As you gain experience, you’ll start to understand both when and how much you can confidently estimate your way to the answer. As you get better, add some variations into the mix. For instance, one problem might have these five answers: (A) −2 (B) −1 (C) 0 (D) 1 (E) 2 Now, these guys don’t look all that far apart but you may still be able to estimate! Two are negative, two are positive, and one is 0. If you can estimate enough to tell that the answer must be negative, then you have a 50/50 shot at getting this right, even if you don’t have enough time or don’t know how to do the problem for real.   Try this problem out, for instance: A salesman bought a total of 50 notebooks, which he sold at 25% profit each. If his total selling price was 812.5 Rs. , what was his cost price for each book? a) 10 b)15 c)13 d)11 Solution – c Now in the above question, considering it is a very easy question, you can tell by the numbers in options itself that it is not going to be 10.The answer cannot be 15 either because the total selling price would have to be a multiple of 5 as well as 3. You can eliminate 11 by using the same divisibility method, and thus you are left with the correct option c. This is a quicker way to solve problems, and when put to practice, can be used for tougher problems too.