Official Guide Explanation:
Data Sufficiency #59




This is just one of hundreds of free explanations I've created to the quantitative questions in The Official Guide for GMAT Review (12th 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: 59
Page: 278
Difficulty: 4 (Moderately Easy)
Category 1: Word Problems > Mixture Problems >
Category 2: Arithmetic > Fractions >

Explanation: Statement (1) is insufficient. We don't know how many students are in section 1 (which would tell us how many students (2/3) represents), and we don't know how many female students are in section 2.

Statement (2) is also insufficient. As with (1), we don't know the size of the given section, nor do we know anything about the other section.

Taken together, the statements are still insufficient. This is essentially a weighted average question. Since (2/3) of the students in one section are female and (1/2) of the students in the other section are female, the number of female students must be between the two fractions. But unless we know how many students are in each section, we don't know where the weighted average falls in between those two fractions. Choice (E) is correct.

Click here for the full list of GMAT OG12 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.