The Knewton Blog

One of the most common areas of frustration for my GMAT students is rate problems.  This seems a general extension of the challenges that word problems overall pose to students, but rate problems are particularly tricky. They require intensive setup and often rely on your realizing an implicit piece of information. As a basic example, suppose I tell you that two joggers run a single lap around the same track.  Aaron runs at a rate… Read more

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We’ll give it to you straight: this strategy for finding the average, or arithmetic mean, of a set of numbers isn’t for everyone. If you master it, though, you can save some serious time on extra-tough GMAT Quant questions. To show you how it works, Jen and Jess have to get a little “mean” in their exploration of averages. Don’t worry: Jen isn’t nearly this mean to Jess in real life.

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In this GMAT video, Rich begins by presenting a sample DS question. The question tests your ability to solve for the value of an expression — without necessarily solving for the variables in that expression. Jess and Rich then go on to explain the best way to solve for one variable in DS problems in which you are given more variables than equations. In addition, they provide a helpful recap of all the tips covered… Read more

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As Jess and Rich explain in this GMAT video, oftentimes on Data Sufficiency problems you’ll be given more variables than you have equations. This happens for two main reasons: You’re just given more variables than equations (you know, because it’s fun) You’re given as many variables as equations, but not all the equations are independent In these cases, you won’t be able to solve for the value of every variable in the system. But —… Read more

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In this video, Jess and Rich cover the basics of independent and dependent equations on Data Sufficiency questions. Here are some of the concepts they discuss: Systems of equations are dependent if one equation can be formed by manipulating and/or combining the others. If no manipulation/combination can create dependent equations, the equations are said to be independent. We need n independent equations to solve for a system with n variables. Dependent equations give us redundant… Read more

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In this video, Jess and Rich cover helpful strategies for solving Data Sufficiency questions involving systems of equations. There are three sample problems to try on your own: pause the video at 00:37, 5:30, and 8:00 to try your hand at each one. After you’ve given each one a shot, stay tuned for Jess and Rich’s step-by-step explanation of the best way to find the answer for each one. You’ll definitely learn some helpful tips… Read more

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In this GMAT video, Jess and Rich show you the best methods for simplifying Data Sufficiency prompts and translating equations into more helpful forms. They present two sample problems (pause the video at 00:21 and 4:10 to try them out for yourself), and then walk you through the most efficient way to arrive at the right answer. Plus, Jess imparts a particularly helpful tip: when Statement I and II provide exactly the same info (even… Read more

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In this video, Jess and Rich talk about “testing cases” in Data Sufficiency problems — i.e. coming up with example numbers and trying them out to see what happens. The goal of this strategy is to help you determine if the DS question prompt is always, sometimes, or never true. As Jess explains, the key with testing cases is to choose different numbers with different properties that still fit the constraints of the prompt, in… Read more

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Let’s face it: exponent rules can be bone dry. Hardly anyone gets excited about building out factor trees. Except for my good friend, RoboMath. With his sweet, autotuned voice and razor-sharp GMAT focus, RoboMath croons his way through tricky Quant questions like he was built for it. Because he was. Nate and I brought RoboMath to life at the latest Knewton Hack Day. Check out the rest of the projects here, and let us know… Read more

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In this video, Rich and Jess kick off a quant session all about Data Sufficiency. In this first portion of the lesson, they cover the “Don’t Solve” strategy for DS — which, as Jess points out, is one of the best math tips around! Remember: for DS problems, all you need to do is evaluate whether you would be able to arrive at the answer using the information provided in each statement; you don’t need… Read more

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