Know when to use the easier Maths

Make your life easier on the CAT: do less Maths.Sure, you’re going to have to do some textbook math on the CAT, but it’s really not a math test. Business schools don’t expect you to have to do paper math in b-school or the real world. Rather, they’re testing how you think about math. And thinking about math in the real world is a lot different than textbook, school-based math. For one thing, the correct answer on the GMAT is never actually a number or a math term. The correct answer is just (A), (B), (C) or (D). How you get to that correct letter doesn’t matter in the slightest. Here is an example that will elaborate this further: Peyman ate 1⁄5 of the chocolates, Rishi ate ¼, and Sharmad ate ½. What fraction of the chocolates are left over? There’s a reason why fractions, decimals, and percents are always taught together: they are just different forms of the same number. For example, 60% = 6⁄10 = 0.6. Different math operations are easier to do with one of these forms than another. Your job is to know which kinds of things are easier to do in which form.In the problem above, you have to add together three fractions.But adding fractions is super annoying because we have to find common denominators. There are three fractions with three different denominators. It’s easier to add numbers in percent or decimal form. For example: 1/5+1/4+1/2=? 20%+25%+50%= 95% Only 5% of the chocolates are left . Oh, wait, they asked for the fractional amount left. That’s okay; convert back! If you have your common conversions memorized, then you already know that 5% = 1⁄20. If not, do this: 5% = 5⁄100 = 1⁄20 What skills did you need to have to do the above? (1) You had to recognize that adding (or subtracting) is easier when using percents or decimals. (2) You had to convert the fractions over. On another problem, this might have been annoying, but this one had “nice” fractions. This wasn’t just luck! You’ll find that, on the CAT, they’re going to set these shortcuts for the people who are trying to find them. (3)You had to remember to convert back to fractional form. But this was worth it to avoid having to find common denominators! And, often, you don’t even have to do that last step. The answers might be so far apart that you can tell which one must be right. Is 5% equal to 1⁄20, 1⁄10, or 1⁄5? You know it’s not 1⁄10 or 1⁄5, so it must be 1⁄20. Alternatively, the answers might actually be in percent form! Glance at them before you solve—that would be a great clue to convert over to percents right away. Or the problem might be written in such a way that you are calculating the actual number of chocolates left over, so you don’t have to convert to fractions again at the end. Let’s say they asked how many chocolates were left and they told that Rishi ate 10 chocolates (along with all of the original info). Rishi ate 25%, so 25% = 10 chocolates. Therefore, 100% = 40 chocolates, and my 5% would amount to 2 whole chocolates. (By the way, if you feel comfortable manipulating percentages, you could go straight from 25% = 10 to 5% = 2. Think about how that shortcut works.)Okay, now that you know that, think for a moment: If the problem requires you to multiply, which form do you want to use? Fractions, decimals, or percents? In this case, it’s easier to use fractions for the same reason that we didn’t want to use them to add. When you have numerators and denominators, you can simplify before you multiply, making the numbers easier to combine. The same is true for division. For example: What is 0.25 divided by 0.375? Same as before: (1) Recognize that you want to use the fraction form. (2) Know your conversions. (3) Convert and solve. As you continue to practice problems, think about where else you can make your life easier by using a different form.