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## Official Guide Explanation:Data Sufficiency #39

Background

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.

Question: 39
Page: 276
Difficulty: 4 (Moderately Easy)
Category 1: Algebra > Linear Equations-One Unk >
Category 2: Arithmetic > Ratio and Proportion >

Explanation: Statement (1), combined with the knowledge that the sample is 80 adults, gives us two equations. If we call the number of adults who are college graduates c and the number who are not n:

c + n = 80

n = 3c

That's two linear equations and two variables. That's always enough to find the variables, so it's sufficient.

Statement (2) is also sufficient. Again, we know:

c + n = 80

This time, we have the difference between the two variables as well:

n = c + 40

Once again, that's two linear equations and two variables. No need to solve, since we know we could solve. Choice (D) is correct.

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