Official Guide Explanation:
Problem Solving #31

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: 31
Page: 156
Difficulty: 5 (Moderate)
Category 1: Word Problems > Rate Problems > Speed
Category 2: Algebra > Equations >

Explanation: This is a very popular type of GMAT question, and a tricky one. It's asking for time, and you can manipulate the traditional rate formula to give you time = ((dist)/(rate)). When working with words per minute, "distance" is a misnomer; it's really more like "amount of work" or, in this case, number of words. The question tells us that his number of words is y and his rate is x words per minute, so time = ((dist)/(rate)) = ((y)/(x)), choice (B). This method may seem more abstract (and perhaps for that reason uncomfortable) compared to plugging in values for the variables, but once you've mastered it, it is considerably faster than your other options.

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.