# GRE Formulas

## Terms

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Formula for % increase

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Formula for % decrease

Where X=the base

What does this equal?

What does this equal

x^2-2xy+y^2=
(x-y)^2
sales price =
(original price) - (%discount)(original price)
total price
(#of items) cost
Distance
Rate x time
30:60:90 triangle
1:2:square rt of 3
45:45:90 triangle leg ratios
1:sr of 2
Pi =
approx 3
nCk
n! / k!(n-k)!
Av Speed =
TD / TT
P(AorB)
P(A)+P(B)-P(A&B)
W/ probab how do you handle exclusions?
Divide factorial of # of events y the product of the exclusions
10% of 30%
.10x.30
Volume of Rectangle Solid
LxWxH
Sum of terms =
Average x # of terms
Slope =
Rise / run
y2-y1 / x2-x1
neg slope = \
pos slope /
STD =
Avg of array (find mean)
diff btwn each & mean
Square differences
Find mean of squared differences
Probability formula
# favorable outcomes / # possible outcomes
6C2
15
4C2
4
16C4 =
16C12 =
multiple of 3
sum of digits is multiple of 3
multiple of 4
last two digits is a multiple of 4
multiple of 6
sum of digits is a multiple of 3 and last digit even
multiple of 9
sum of digits is a multiple of 3 and sum of last two digits are multiple of 4 ie 135
% formula =
part = percent x whole
Percent increase =
amount of increase / original whole then x 100
Percent decrease =
amount of decrease / original whole then x 100
What is the average formula
avg = sum / # of terms

sum = avg x # of terms
Avg of evenly spaced #s
avg of min + max
How do you count consecutive numbers?
Max - Min +1
Ratio formula
ratio = of / to

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