You can crack the scary looking GMAT Math section with a help of some friendly little companions. Little – because many of them will take you back to your school days. Friendly – because you’ve already played a lot with them as a kid.
But that was way back in time, when you never imagined that the teacher was writing on the backboard would be so important. No worries. We’ll get you back to speed in the next few minutes.
Here’s a cheat sheet of GMAT Maths formulas covering arithmetic, algebra and geometric concepts covered in the GMAT syllabus. You can bookmark it for reference and use it when you get stuck with some difficult GMAT maths questions. Though it’s not exhaustive, it’s a comprehensive enough list of math formulas to solve a big range of GMAT quant questions.
Some of these are rules. They are basic rules and protocols that apply to numbers.
PEMDAS: Parenthesis – Exponents – Multiplication – Division – Addition – Subtraction
Maximum ‘silly mistakes’ in GMAT maths happen because of not following this rule strictly. So we are placing this at the very top. Memorise this and make it second nature.
Here’s another set of very simple rules that often cause a lot of distress after you’ve realised why you got the question wrong.
[Positive Number] X [Positive Number] = [Positive Number]
[Positive Number] X [Negative Number] = [Negative Number]
[Negative Number] X [Negative Number] = [Positive Number]
[Positive Number] / [Positive Number] = [Positive Number]
[Positive Number] / [Negative Number] = [Negative Number]
[Negative Number] / [Negative Number] = [Positive Number]
[Odd Number] + [Odd Number] = [Even Number]
[Odd Number] – [Odd Number] = [Even Number]
[Odd Number] + [Even Number] = [Odd Number]
[Odd Number] – [Even Number] = [Odd Number]
[Even Number] + [Even Number] = [Even Number]
[Even Number] – [Even Number] = [Even Number]
[Odd Number] X [Odd Number] = [Odd Number]
[Odd Number] X [Even Number] = [Even Number]
[Even Number] X [Even Number] = [Even Number]
This is the reverse of exponents. With the square root (√) symbol we are trying to find a number that should be multiplied by itself to get the answer.
For example, √100 = 10
A cube root requires the same number to be multiplied thrice.
3√64 = 4 [because 4 X 4 X 4 = 64]
n! = n * (n-1) * (n-2) * … * 2 * 1
0! = 1
Permutation formula: nPr = n! / (n-r)!
Combination formula: nCr = n! / (r!)(n-r)!
Proability = Number of favourable outcomes / Number of all possible outcomes
Probability of events A & B happening = Probability of A X Probability of B
Probability of either event A or B happening = Probability of A + Probability of B
Distance = Speed * Time
Wage = Rate * Time
|x| depicts the absolute value (or magnitude). Here are some rules and formulas for absolute values.
|x| = x
|-x| = x
|x| = |-x|
|x| ≥ 0
|x| + |y| ≥ |x+y|
In the expression xn, ‘x’ is the base and ‘n’ is the exponent. The way to interpret is that the base ‘x’ gets multiplied ‘n’ times.
Some rules and formulas that apply to base/exponents:
0n = 0
1n = 1
x0 = 1
x1 = x
(x)-n = 1 / xn
xm * xn = xm+n
xm / xn = xm-n
(xm)n = xm*n
(x/y)n = (x)n/(y)n
Square: Area: (length)2 | Perimeter: 4(length)
Rectangle: Area: length X breadth | Perimeter: 2(length) + 2(breadth)
Parallelogram: Area: base X height | Perimeter: 2(base) + 2(height)
Circle: Area: πr2 | Circumference of a circle: 2πr [where Pi (π) = 3.14]
Triangle: Area: (1/2) length X breadth
Pythagoras Theorem (for right angled triangles): (base)2 + (height)2 = (hypotenuse)2
Rectangular prism: length X breadth X height
Cone: (1/3) πr2h
Pyramid: (1/3) base length X base width X height
If you prefer downloading free pdf cheat sheets, instead of referring to them online, here’s a list of GMAT prep resources for you.
From Aristotle Prep: This is a detailed (31 page) PDF file which covers many GMAT quant formulas and concepts. Click here to download.
From GMAT Hacks: Use this one after you’ve brushed up on your concepts, as the file has GMAT math sample problems for you to test your newly revised knowledge. Click here to download
Or if you have 20 minutes to spare, you could try our short free online GMAT test. It’s got sample quant and verbal questions.
Read this next:
– All topics in the GMAT syllabus
Source: GMAT Club, Aristotle Prep, other GMAT prep sites.