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Land Your Score: Backsolving in Quantitative Reasoning

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Need to improve your Quantitative Reasoning skills?

Use critical thinking to optimize your GMAT problem-solving strategy.

While making your way through the Quantitative Reasoning section, it’s easy to forget that the GMAT is a critical thinking test, not a math test. Using strategies to save time and minimize errors is rewarded on Test Day.

Use backsolving for Quantitative Reasoning efficiency

One easy-to-overlook GMAT strategy is backsolving—plugging in the answer choices. Working backwards from an answer choice takes practice; you want to use it on practice problems until you feel comfortable deciding how and when to use this strategy.

Here is an example of a great problem for backsolving:

Jamal lives x blocks from his office. He can walk to his office at a rate of 1 block per minute, and he can ride his bicycle to his office at a rate of 3 blocks per minute. If it takes him exactly 10 minutes more to walk to his office than to ride his bicycle, then x equals

  • 4
  • 7
  • 10
  • 15
  • 20

Recognize opportunities to backsolve problems

GMAT questions that are good candidates for backsolving often have one or more variables in the question. When the answer choices are numbers that represent possible values for those variables, you can craft an equation or expression to plug them into.

This question asks you to solve for x, and the answer choices are integers, so this is a great problem to strategically solve instead of using algebra. In particular this word problem sets up a realistic scenario, so you can plug in the answer choices without creating equations for the two commuting methods.

Narrow down your options

For this Quantitative Reasoning example problem, break down the situation in the problem. Jamal can walk to work at 1 block per minute, and he can bike at 3 blocks per minute. You also know that the difference in the time it takes to walk and bike is 10 minutes. Using your critical thinking skills, you can eliminate answer choices that cannot work in this situation: The distance has to be more than 10 blocks to account for the 10-minute differential. This means you can eliminate 4, 7, and 10 as possible answers.

You can also rule out answer choices not divisible by 3, since the time it takes for Jamal to ride his bike must be a whole number of minutes in order for the difference to be 10 minutes. Even if you don’t recognize this, you’ve already narrowed it down to two choices. So pick one and plug it in!

Plug and play your answer choice

If x=15, that means Jamal lives 15 blocks from his office. If he walks 1 block per minute, it takes 15 minutes to walk. If he bikes 3 blocks per minute, it takes 5 minutes to ride. Is the difference between the two 10 minutes? Why, yes it is! Select 15 as the answer and move on.

Often backsolving allows you to use critical thinking (and common sense) to find the correct answer in Quantitative Reasoning instead of using algebra. Many test takers immediately try to come up with equations, but with practice you will be able to decide whether this strategic approach makes more sense.

Looking for more Quantitative Reasoning problems to try? Sign up to take a free online GMAT practice test today.

The post Land Your Score: Backsolving in Quantitative Reasoning appeared first on Business School Insider.