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Welcome to the fifth and final installment of our Fast Math series. (Miss any earlier ones? Start here. )

Make your life easier on the GMAT: do less Math. (Yes, with a capital-M. ☺ ) I use Math-with-a-capital-M to mean formal, textbook math.

Sure, you’re going to have to do some textbook math on the GMAT, 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), (D), or (E). * How * you get to that correct letter doesn’t matter in the slightest.

Okay let’s dive into our 5 th Principle for Fast Math!

Principle #5: Know when to use fractions, or decimals, or percents.

Peyman ate 1 ⁄ _{ 5 } of the chocolates, Rishi ate ¼ , and Sharmad ate ½ . What fraction of the chocolates are left over for me?

(These are students in one of my current classes. Hi, guys!)

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.

You already know all that, right? So what’s my point?

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, I have to add together three fractions.

But wait! Adding fractions is super annoying because we have to find common denominators. There are three fractions with three different denominators. Ugh!

It’s easier to add numbers in percent or decimal form. For example:

Only 5% of the chocolates are left for me. (And I hope you enjoy my beautiful artwork.

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