Official Guide Explanation:
Data Sufficiency #D46

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.

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

Solution and Metadata

Question: D46
Page: 25
Difficulty: 5 (Moderate)
Category 1: Arithmetic > Percents > other
Category 2: Arithmetic > Descriptive Statistics > Average

Explanation: The information given includes the average of the 10 employees' salaries last year, from which we could determine the total salary paid to the 10 employees. To find the average salary this year, we need to know how much each of the employees' salaries changed.

Statement (1) is insufficient. We don't know what happened with the other 2 salaries, and we don't know how much of the total those 8 salaries made up.

Statement (2) is also insufficient. We don't know about the other 8 salaries, and we don't know what fraction of the total those 2 salaries represented.

Taken together, the statements are still insufficient. While we know that 8 salaries increased by 15% and 2 salaries stayed the same, we don't know how much money is represented by the 8 salaries and the 2 salaries. The total salary is about $430,000; if the 2 salaries that stayed the same totaled $30,000, the resulting salary this year is much greater than if the two salaries that stayed the same totaled $130,000. Choice (E) is correct.

Click here for the full list of GMAT OG12 explanations.

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.