Percentage Change Formula

[vadremc]

In the Manhattan GMAT Prep Studyguide 2007 edition, on page 57, there is a percentage change formula at the very end of the page. I know that change/original is the formula, however how would you calculate 702/729 logically and timely? Is there a shortcut to calculating this number? Please outline the steps. Thx. :)

[mdinerstein]

Hi vadremc,

Which book did you find this issue in? In the meantime, I will forward this post to an Instructor who will provide you with a more detailed answer.

Good luck studying!

Best,

Michael Dinerstein
Marketing & Student Services Associate
michael@manhattangmat.com
800-576-4628
212-721-7400

[StaceyKoprince]

I'm guessing this might have come from the Fractions, Decimals and Percents book? (We have 5 math books!)

First, know that the real test will not make you simplify 702/729 to any very specific level - you don't have enough time for that. Some of the problems in the strategy guides are designed simply to test your ability to understand the math, more like a math textbook. They aren't written as GMAT-type questions.

If you did need to simplify something like that on the GMAT, you would be able to estimate based on the answer choices. So you'd change 702 to 700, and then you'd like to change 729 to something close that also contains some of the same factors as 700.

So you could try 700/730, which simplifies to 70/73, which is almost, but not quite, 1. So whichever choice is a little less than 1 would be your answer.

For GMAT-type questions, always check out your answer choices before you start to solve - that can help give you ideas about how you want to solve! Especially if the math looks annoying - chances are you can estimate.