You may remember this formula, one of the sleekest factoring tricks in all of algebra: This formula, called “the difference of two squares” formula, is a favorite of standardized test writers. A simple enough pattern: see if you can detect where it shows up in the following challenging problems. 1) = (A) (B) (C) […]

# Archive | Algebra

## Variables in GMAT Answer Choices: Algebraic Approach vs. Numerical Approach

Fact: On GMAT Problem Solving, some of the prompts will state quantities in terms of variables, and then expect you to answer in terms of those variables. Such questions are known as “variable in the answer choice” questions (or VICs in some circles). Fact: There are two basic strategies you can use to solve these: […]

## GMAT OG Case Study: Problem Solving Practice Problem #163

Here is the problem that appears in the OG, 12th Edition: Problem Solving Practice Problem #163 This year Henry will save a certain amount of his income, and he will spend the rest. Next year Henry will have no income, but for each dollar he saves this year, he will have 1 + r dollars […]

## Breakdown of GMAT Quant Concepts by Frequency

Magoosh’s very own Mike McGarry, GMAT/Math Teacher/Tutor/Foosball player extraordinaire, went through 5 different sets of Official GMAT Practice Material and tallied questions based on the subject material they tested to find the most common GMAT questions. Here are the samples of Official Material he used to figure out the GMAT Quant breakdown: 1.GMAT Official Guide […]

## Percent Change Problems on the GMAT

This is, among other things, a case study of one of the harder Data Sufficiency problems in the OG. Percents as Multipliers You can find several good tips on percent problems at this post. The most relevant here is the idea of a percent as multiplier. To change a percent into a multiplier: (a) change […]

## Comparing Ratios on the GMAT

Among other things, this post is a case study of an OG DS question: OG 12th Edition, Data Sufficiency Practice Problem #23 Here is the problem that appears in the OG: 23) If p1 and p2 are the populations and r1 and r2 the number of representatives of District 1 and District 2 respectively, the […]

## GMAT Official Guide Practice Problem: Francine’s Trip

OG 12th Edition, Problem Solving Practice Problem #149 Here is the problem that appears in the OG: During a trip, Francine traveled x percent of the total distance at an average speed of 40 miles per hour and the rest of the distance at an average speed of 60 miles per hour. In terms of […]

## GMAT Quadratic Inequalities

A Case Study of a Problem: OG 12th Edition, Problem Solving Practice Problem 173 Here is the problem that appears in the Official Guide: 173) Which of the following describes all values for which > OK, this is a quadratic inequality, a relatively advanced math topic for the GMAT, one with a relatively low […]

## GMAT Math: Understanding Absolute Values

GMAT Math will ask you about absolute values. Mastering what the GMAT asks about them requires sophisticated understanding. Somewhere along the line, perhaps in middle school, you probably learned: |positive| = positive and |negative| = positive In other words, the equation |x| = 5 has the solution: x = 5 or x = […]