Official Guide Explanation:
Data Sufficiency #50




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: 50
Page: 277
Difficulty: 5 (Moderate)
Category 1: Arithmetic > Sets > 2 sets
Category 2: Word Problems > Sets >

Explanation: Judging from the question, this looks like a question that involves overlapping sets: there will be some directors of Companies K and R that overlap and others who don't. Statement (1) is not sufficient, but it does provide some information: 17 = (K directors) + (R directors) - (directors in both K and R). Statement (2) is also insufficient, as it gives no indication how much overlap there is.

Taken together, the statements are sufficient. According to (1): 17 = (K directors) + (R directors) - (directors in both K and R). (2) fills in some of those gaps:

17 = 12 + 8 - overlap

17 = 20 - overlap

overlap = 3

Thus, the correct choice is (C).

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.