Official Guide Explanation:
Data Sufficiency #9




This is just one of hundreds of free explanations I've created to the quantitative questions in The Official Guide for GMAT Quantitative Review (2nd ed.). Click the links on the question number, difficulty level, and categories to find explanations for other problems.

These are the same explanations that are featured in my "Guides to the Official Guide" PDF booklets. However, because of the limitations of HTML and cross-browser compatibility, some mathematical concepts, such as fractions and roots, do not display as clearly online.

Click here for an example of the PDF booklets. Click here to purchase a PDF copy.


Solution and Metadata

Question: 9
Page: 153
Difficulty: 4 (Moderately Easy)
Category 1: Arithmetic > Ratio and Proportion >
Category 2: Algebra > Linear Equations-Two Unk >

Explanation: The question tells us that the ratio of ((X)/(Y)) = (5/6) . We're looking for the value of Y.

Statement (1) is sufficient. Given that X = Y + 80, we have two equations, between this statement and the ratio given in the question. No need to solve; with two equations and two variables, we can find either variable.

Statement (2) is also sufficient. Here, the second equation is X + Y = 880. Again, with two equations and two variables, we can solve for Y. Choice (D) is correct.

Click here for the full list of GMAT Quant Review explanations.


You should follow me on Twitter. While you're at it, take a moment to subscribe to GMAT Hacks via RSS or Email.

Total GMAT Math

The comprehensive guide to the GMAT Quant section. It's "far and away the best study material available," including over 300 realistic practice questions and more than 500 exercises!
Click to read more.