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## Official Guide Explanation:Problem Solving #125

Background

This is just one of hundreds of free explanations I've created to the quantitative questions in The Official Guide for GMAT Quantitative Review (2nd 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: 125
Page: 78
Difficulty: 5 (Moderate)
Category 1: Algebra > Linear Equations-One Unk >
Category 2: Arithmetic > Properties of Integers > Factors and Multiples

Explanation: If x is an integer, then 3x is a multiple of 3. To rephase the equation, y is 2 greater than a multiple of 3. That means that y itself cannot be a multiple of 3. Since the only numbers that are divisible by 6 are multiples of 3, y cannot be divisible by 6, which means that (C) is correct.

If you aren't able to make those connections, it is always an option to come up with a series of possible values for y: when x = 1, y = 5, when x = 2, y = 8, etc. Eventually, that series of numbers will eliminate four of the five choices. However, it's much quicker to think about the set of possible y values more abstractly.

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