Official Guide Explanation:
Data Sufficiency #107




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: 107
Page: 282
Difficulty: 4 (Moderately Easy)
Category 1: Arithmetic > Discrete Probability >
Category 2: Arithmetic > Fractions >

Explanation: Since there are three colors of chips in the box, the probability that a selected chip is white or blue is 1 minus the probability that it is red.

Statement (1) is insufficient: the probability of white or blue is the sum of the probability of white and the probability of blue, and this only gives us one of those. Statement (2) is sufficient: the probability we're looking for is (1 - red), so given the probability of red, we can find the probability of white or blue. Choice (B) 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.