GRE Quant Formulas

distance

D = RT

a^m aⁿ

a^m+n

a^m/aⁿ

a^m-n

(a^m)ⁿ

a^mn

a⁰

1

a^-n

1/aⁿ

area of a circle

πr²

circumference of a circle

2πr or πd

45-45-90 triangles sides

1,1, and √2

30-60-90 triangles sides

1, √3, 2

slope equation

m = (y₂ - y₁)/(x₂ - x₁)

quadratic formula

x= -b ± √(b² - 4(a)(c)) / 2(a)

rate

= 1/x

Arithmetic formula (specific for arithmetic sequence problems)

= n/2 (A_first + A_last)

Geometric sequence formula (specific for geometric formulas)

An = A1 x r^n-1

what is a unit digit

the right most number of the number (excluding decimals)

Simple interest

you earn interest only on the original starting amount, so the increase is the same each period

Compound interest

you earn interest on both the starting amount and the interest already added, so the amount grows faster over time

least common mutliple (LCM)

The smallest number that BOTH numbers divide into evenly

greatest common factor (GCF)

GCF = the largest number that divides BOTH numbers evenly

greatest prime factor

the largest prime number that divides the number.

area of a trapezoid

[(b₁ + b₂) / 2 ] x height

how to find standard deviation

• find the mean

• subtract each number of the datasets distance from the mean

• square those values

• find the new mean of those numbers