Tag Archives: quantitative strategy lesson 2

Video: Solving for One Variable Among Many in DS Questions


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 in this quantitative strategy lesson — if you haven’t watched all the videos, be sure to check them out!

Video: How to Solve for the Value of an Expression (Without Solving for its Variables!)


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 — don’t be fooled! This doesn’t necessarily mean that E is the right answer. Sometimes, you may be able to solve for the value of an expression involving multiple variables — without actually knowing the value of those variables. Confused yet? Check out the video for a sample problem and a super helpful explanation!

Want more DS help? Check out more installments of this quantitative strategy lesson!

Video: The Basics of Independent and Dependent Equations


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 information, so they don’t help us solve for all variables.
  • If we try to solve a system with dependent equations, we will find that doing so is impossible. We will end up with an identity.

Check out the video for more detailed explanation and examples! For more Data Sufficiency help, be sure to check out past installments of this quantitative strategy lesson.

Video: Three Classic DS Questions Involving Systems of Equations


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 and shortcuts along the way.

For more Data Sufficiency strategies, tune in to the rest of this quantitative strategy lesson and stay tuned for future videos!

Video: How to Simplify Data Sufficiency Questions


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 if it comes in a slightly different form!), the only two possible answers are D and E.

Watch the video for more, and be sure to check out previous installments of this quantitative strategy lesson!

Video: Testing Cases in Data Sufficiency


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 order to see if they produce varying outcomes. If they do, then the statement is insufficient!

Check out the video for more on this important strategy and to try out a sample problem on your own.

Eager for more DS help? Check out the other installments of this Quantitative Strategy lesson!

Video: Don't Solve Data Sufficiency Problems!


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 to waste time actually finding the answer!

In order to illustrate the importance of this time-saving strategy, Rich and Jess walk you through two sample problems. Pause the video around 1:25 for the first question and 5:25 for the second to try the questions out for yourself first.

Stay tuned for future installments of this quant lesson, coming soon!