Friday, April 26, 2013

GRE Math Formulas Cheat Sheet

By Revised GRE on 10:56 AM



Before walking into the GRE, it is a good idea to know the following formulas/tidbits. In fact, not knowing the information below can seriously hurt your chances of answering a question correctly.
At the same time, while this is a very useful cheat sheet, do not just memorize formulas without actually applying them to a question. Often students will see a question and will assume that a certain formula is relevant. This is not always the case. So make sure you practice using the formulas so you will know when they pertain to a question.

Interest

Simple Interest: V=P(1+rt/100), where P is principal, r is rate, and t is time
Compound Interest: V=P(1+r/{100n})^nt, where n is the number of times compounded per year

Work Rates

{1/TotalWork}={1/WorkRate1}+{1/WorkRate2}

Sets

{A+B}-{({A}bigcup{}{}{ B})}

Distance, Rate, and Time

D=rt, Distance=Rate*Time

Circles

Area=pi{r}^2
Circumference=2pi{r}
Arc Length={x/360}2{pi}r
Area of sector={x/360}{pi}r^2

Squares

Perimeter=4s, where s = side
Area = s^2

Rectangles

Area = l*w, where l = length and w = width
Perimeter = 2l+2w

Trapezoids

{{Base1+Base2}/2}*height

Polygons

Total degrees = 180(n-2), where n = # of sides
Average degrees per side or degree measure of congruent polygon = 180(n-2)/n

The Distance Formula

sqrt{({x_2}-{x_1})^2+({y_2}-{y_1})^2}

Prime numbers and integers

1 is not a prime. 2 is the smallest prime and the only even prime.
An integer is any counting number including negative numbers (e.g. -3, -1, 2, 7…but not 2.5)

Fast Fractions

{1/x}+{1/y}={x+y}/{xy} i.e. {1/2}+{1/5}={2+5}/{2*5}=7/10

Divisibility

3 : sum of digits divisible by 3
4 : the last two digits of number are divisible by 4
5 : the last digit is either a 5 or zero
6 : even number and sum of digits is divisible by 3
8 : if the last three digits are divisible by 8
9: sum of digits is divisible by 9

Combinations and Permutations

nCr={n!}/{r!(n-r)!}   n is the total number, r is the number you are choosing
nPr={n!}/{(n-r)!}

Probability

Probability of event = {number of ways that fit the requirement}/{number of total ways}