Posted on
07
Sep 2021

How-to GMAT: No Calculator? Use These Mental Math Tips Instead

The GMAT is an exam largely focused on numbers and numerical data. And while doing math on the GMAT should be avoided sometimes it is inevitable. True, the test-taker is given a calculator for the duration of the Integrated Reasoning section but the same cannot be said for the Quantitative Reasoning Section.

The Basics

Before explaining any methods for dividing and multiplying with ease, let’s make sure we have revised a few simple rules:

• Numbers with an even last digit are divisible by 2 – 576 is and 943 is not;
• Numbers with a sum of digits divisible by 3 are also divisible by 3 – 3,465 for example (3+4+6+5=18);
• If the last 2 digits of a number a divisible by 4, the number itself is divisible by 4 – 5,624 for example (because 24/4=6);
• Numbers with last digit 0 or 5 are divisible by 5;
• Numbers that can be divided by both 2 and 3 can be divided by 6;
• Similar to numbers divisible by 3, numbers divisible by 9 must have a sum of digits divisible by 9 – 6,453 for example;
• If the last digit of a number is 0 it is divisible by 10;

With that out of the way, we can move onto some more advanced mental math techniques.

Avoid division at all costs

Don’t divide unless there is no other option. And that is especially true with long division. The reason why long division is so perilous is that it is very easy to make a careless mistake as there are usually several steps included in the calculation, it takes too much time, and to be honest, few people are comfortable doing it.

Fortunately, the GMAT doesn’t test the candidates’ human-calculator skills but rather their capacity to think outside the box and show creativity in their solution paths, especially when under pressure – exactly what business schools look for.

However, sometimes you cannot avoid division, and when that is the case remember: Factoring is your best friend. Always simplify fractions especially if you’ll need to turn them into decimals. For example, if you have 234/26 don’t start immediately trying to calculate the result. Instead, factor them little by little until you receive something like 18/2 which is a lot easier to calculate.

A tip for factoring is to always start with smaller numbers as they are easier to use (2 is easier to use compared to 4, 6, or 8) and also look for nearby round numbers.

If you have to calculate 256/4 it would be far less tedious and time-consuming to represent 256 as 240+16 and calculate 240/4+16/4=60+4=64. Another example is 441/3. If we express it like 450-9 it is far easier to calculate 450/3-9/3=150-3=147.

Dividing and Multiplying by 5

Sometimes when you have to divide and multiply by 5 (you’ll have to do it a lot) it would be easier to substitute the number with 10/2. It might not always be suitable for your situation but more often than not it can be utilized in order to save some time.

Using 9s

With most problems, you could safely substitute 9 with 10-1. For example, if you have to calculate 46(9) you can express it as 46(10 – 1) which is a lot more straightforward to compute as 46(10) – 46(1) = 460 – 46 = 414

You can also use the same method for other numbers such as 11, 8, 15, 100, etc:

18(11) = 18(10 + 1) = 180 + 18 = 198

28(8) = 28(10 – 2) = 280 – 56 = 224

22(15) = 22(10 + 5) = 220 + 110 = 330

26(99) = 26(100 – 1) = 2600 – 26 = 2574

Dividing by 7

The easiest way to check if a number is divisible by 7 is to find the nearest number you know is divisible by 7. For instance, if you want to check if you can divide 98 by 7 you should look for the nearest multiple of 7. In this instance either 70, 77, or 84. Start adding 7 until you reach the number: 70 + 7 = 77 + 7 = 84 + 7 = 91 + 7 = 98. The answer is yes, 98 is divisible by 7 and it equals 14

Squaring

When you have to find the square of a double-digit number it might be easier to break the number into components. For example, 22^2 would be calculated like this:

22^2
= (20 + 2)(20 + 2)
= 400 + 40 + 40 + 4
= 484

Similarly, if you have to find the square of 39 instead of calculating (30 + 9)(30 +9) you could express it like this:

39^2
= (40 – 1)(40 – 1)
= 1600 – 40 – 40 + 1
= 1521

You can use the same approach when multiplying almost any double-digit numbers, not only squaring. For example 37 times 73:

(40 – 3)(70 + 3)
= 2800 + 120 – 210 – 9
= 2701

Conclusion

This ends the list of mental math tips and tricks you can utilize to make the Quant section a bit less laborious. Keep in mind that no strategy or shortcut would be able to compensate for the lack of proper prep so it all comes down not only to practicing but doing so the right way.

For more information regarding the GMAT Calculator, GMAT Calculator & Mental Math – All You Need To Know, is a very insightful article to read.

Posted on
27
Jul 2021

GMAT Calculator & Mental Math – All You Need To Know

Author: Apex GMAT
Contributor: Ilia Dobrev
Date: 27 July, 2021

Are you allowed to use a calculator on the GMAT? While this may seem as a pretty straightforward question to answer, it does deserve a separate blog post as it hides details that are vital for achieving a top GMAT score not only on the quantitative section, but on the exam as a whole.

Well, the answer is both Yes and No. This article aims to examine the different scenarios where you are allowed to use such a device and how you can make full use of its potential. But, if you are used to doing math with a calculator, do not worry as we have compiled a list of some mental math techniques that you can use to your advantage and even save much important time while still being spot-on with your answers.

Calculator on the GMAT | Explained

• You are not allowed to bring your own calculator to the GMAT exam.
According to the GMAC, no personal items are allowed in the exam room of any of the certified test centers.
• You cannot use a calculator on the Quantitative section of the GMAT.
Despite the fact that we are so used to using calculators to help us with arithmetic operations, you should not feel intimidated that you are not allowed to use any type of calculator on the GMAT Quantitative section. However, you will be provided with a blank canvas by the proctor of the exam where you will have plenty of space to practice to manually compute any calculations, if needed.

You should not worry as the GMAT exam is not designed to test you on complicated mathematical operations or complex calculations. Instead, the quant section draws from secondary-level math skills like basic algebra and geometry, which are mastered in high school, to test other kinds of abilities like critical thinking, logical reasoning, and problem-solving. In fact, the majority of the Quant questions can (and should) be answered without any calculations beyond estimation. A typical example of how you can use mental math to get to the right answer while saving precious time on the GMAT is the Movie Night combinatorics problem. Another type of common GMAT quant questions are data sufficiency problems, which are also more about reasoning than  calculations. You’ll only need to do basic calculations and can rely on estimation for anything more complicated. If you have to do the math, the GMAC usually keeps the numbers simple and avoids decimals. When you see large numbers or complex fractions, then it’s a good bet that there’s an easier solution path to embark on other than calculating.

Surprisingly or not, a calculator will be provided for use during the GMAT Integrated Reasoning section of the test. This GMAT calculator has the standard basic functions, CE (clear entry) button, C (clear) button, an sqrt function, a % (percentage) button, and a 1/x button that calculates the reciprocal of the entry currently on the screen. Also, there is a row with the standard memory functions

• MS (memory store) stores the current entry in the calculator’s memory for subsequent use.
• MR (memory recall) displays the latest number stored in the calculator’s memory so that it can be used for the next calculations.
• M+ (memory addition) adds the current entry to the value that is currently stored in the calculator’s memory. This button is helpful when you need to add a long series of numbers and don’t want to retype each one.
• MC (memory clear) erases whatever is in the current memory. You should click this button before every new calculation scenario.

Survival Tips & Tricks

Do not overuse the IR calculator.

While you are provided with a basic GMAT calculator during the Integrated Reasoning section, you might not want to use it too often as you’ll waste more time than you’ll save. You can also apply the solution paths you are using in the Quant section to some problems in the Integrated Reasoning section.

Constantly practice Mental Math operations.

A huge morale boost is that mental math operations are easy to learn with some practice. You can add, multiply, subtract, and divide when you pay bills, check out at the grocery store, calculate a tip, etc. without using a calculator.

Make accurate estimations

The key to saving a considerable amount of time on the GMAT exam is efficiency in estimations. Transform numbers to less unwieldy figures like 0 or 5 for the purpose of calculations. You can then browse the answer choices to see which is closest to your preliminary estimate.

Do not use a calculator when you are prepping for the GMAT quant section.

This is a great way to practice mental math operations outside the daily life operations. The test setting and quant context will let you get used to this environment so that you know what to expect on test day.

Familiarize yourself with a basic GMAT calculator and do use its Memory functions.

As this will be your only technical aid during the GMAT Integrated Reasoning section, you’d better spend some time making the most out of it. Especially when you are pressed by time, memorizing calculated values for further operations in the calculator’s memory can be crucial for staying on track with a healthy exam pace.

Guide yourself by looking at the answer choices.

Looking at the answer choices can immediately permit you to eliminate a couple of options. Even if you are pushed by time, you can easily make a more educated decision depending on your reasoning that will boost the chances of picking the correct answer.

Do not freak out if you see large numbers.

Remember that the people who stand behind the GMAT are aware that they are designing questions that are supposed to be answered without using a calculator. This also keeps the arithmetic from being too difficult and gives you the opportunity to apply a more straightforward approach.