For GMAT Prep, Inequalities problems can be some of the toughest problems to master. Sometimes, the candidates may even master the inequalities during GMAT practice and mock tests. However, during the GMAT exam, when faced with the pressure of time and accuracy, they tend to make mistakes. One of the most common mistake made by the candidates in inequalities problem is “Cross Multiplication”:

“Cross Multiplication of unknowns” is the most common problem candidates make in inequalities problems.

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How can cross-multiplication lead to a mistake? Lets us elaborate further with the help of a video:

Trouble watching this video? Watch it here: GMAT Inequalities: Common mistake

Why is cross-multiplication is such a common problem? Because you are used to solving equations and in equations, you are almost always allowed to cross-multiply. So much so that cross-multiplication often becomes an instinct. However, in inequalities cross-multiplication can lead to problems unless you “know” the sign of the variables.

** Final tip: **When faced with an inequality problem during GMAT Math section of the mock or real GMAT exam – DO NOT Cross Multiply variables, unless you are confident that the variable is positive.

Unless you are confident that a variable is positive, DO NOT cross-multiply in an inequalities problem.

From now on, when you practice inequalities questions, pay special attention to:

- How often do you tend to cross-multiply to get to a solution?
- Did your cross-multiplication result in a mistake?
- If not – why not? (Sometimes questions identifies the variable as positive or negative)
- Note these in a log. Keeping a log will help you understand if the cross-multiplication is causing a recurring problem
- Practice caution while cross-multipliplying whether solving equations or solving inequalities to avoid mistakes

We hope this paragraph helps you get a better score on GMAT. For more tips and tricks about GMAT Inequalities, please visit the GMAT Math Inequalities section.