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Mental Math on the GRE

With the advent of the calculator on the GRE, some would say the days of knowing how to do mental math are obsolete. While you could rely on the calculator for the entire test, doing so may actually slow you down. Indeed a facility mental math will save you a lot of time, and may help you avoid any careless slip of the fingers.


Focus on the problem

Momentarily stepping out of the problem, so to speak, to attend to the calculator can interrupt the flow. You may forget exactly what the number pertained to. Was it the answer? Or was it one of many calculations you need to do to arrive at the answer? If it is the latter, then you may forget your place and have to start over.



By constantly relying on the calculator you can get a case of calculator-itis. Even easy computations has you running for the on-screen calculator. While you may be fast with your fingers, being able to calculations like 14 x 5 in your head will be a lot of faster. And with so many such calculations, those few seconds per calculation adds up to quite a lot over the course of the test.


Slippery fingers

Sure, we are all prone to mental math mistakes. But we are also prone to entering in the wrong numbers, especially under timed conditions. If it is a simple calculation, sharpen your calculator brain—don’t let 17 x 3 = 42, because of a simple slip of your finger.


The power of approximation

Some questions may seem daunting, but with just a little mental approximation you can quickly get the answer. What is 15% of 50,200? Well, it’s a little bit greater than 7,500. If only one answer is close to 7,500 then you save yourself the time of having to enter the number into the calculator.

You may balk thinking that you’d prefer the accuracy, but remember working out your mental math muscle before the test will help you become far more adept at doing quick calculations in your head.



Using a calculator makes sense when you are dealing with big numbers, especially in the case of data input. But if you are dealing with smaller sums (say 20 x 12), then relying on math can save you a lot of time. And you won’t have to worry about any slippery fingers.


By the way, students who use Magoosh GRE improve their scores by an average of 8 points on the new scale (150 points on the old scale.) Click here to learn more.

7 Responses to Mental Math on the GRE

  1. Sarah January 15, 2016 at 2:31 pm #

    Do you know any good apps for android that will allow me to practice my mental math?

    • Jitesh Dange February 8, 2016 at 8:38 am #

      Hi Sarah,

      You can play sudoku.

  2. Ram March 20, 2014 at 9:13 pm #

    Very helpful. Thanks a ton Chris!

    • Chris Lele
      Chris Lele March 21, 2014 at 10:19 am #

      You are plenty welcome 🙂

  3. Gaia June 13, 2012 at 4:53 pm #

    Hi Chris,

    I have an unrelated question to ask you. I recently got my hands on this huge GRE book that contains “27 previously administered full-length tests.” The problem is that it’s from 1998. Although the questions won’t be in the Revised GRE format, can I still use the the problems for practicing?


    P.S. Magoosh is AMAZING. Thank you thank you thank you!

  4. Sammy June 13, 2012 at 10:50 am #

    Really helpful post, Thanks Chris!
    PS – I think you inadvertently added another zero at the end of 7500. =)

    • Chris Lele
      Chris June 13, 2012 at 3:48 pm #

      So much for my mental math :).

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