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# GRE Math Formulas and Definitions

## Terms

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LCD
1. Write prime factors out
2. Cross out any PF in second denom. that appears in first denom
3. Multiply remaining factors
Averages:
Mean
Median
Mode
Mean: Sum of #s/ # of elements
Median: Middle
Mode: Most often
Average of X #s = Y...
X = number of elements
Y = the average
Therefore, if sum/X = Y
Sum = XY
Ratio/Proportion
Ratio- compares 2 #s
Proportion- two equal ratios
(-X)^2,4,6,8,10...
(-X)^1,3,5,9...
Even power- Always positive
Odd power- Always negative
Binomial Squares
FOIL- First, Outer, Inner, Last
Linear Equation
-Highest power of any variable is 1
-Solve by isolating variable on 1 side
-At least one variable is raised to 2nd power
-Set one side of equation = 0
-Factor out non-zero side
-Set each Factor = 0 and solve
Area of Triangle
A = 1/2bh
Rectangle Area, Perimeter
A = lw
P = 2l + 2w
Circle
A = Pi r^2
C = Pi d or 2Pi r
Length of Arc
Arc AB = (X/360) x 2Pi r
Pi
3.14 or 22/7
Inscribed Angle
1/2 measure of intercepted Arc
Surface Area of a Cube
S = 6a^2
Volume, SA
V = lwh
SA = sum of areas of all faces
Distance
d =
Radical( x1-x2)^2 + (y1-y2)^2
Midpoint
MP =
__x1+x2__ , __y1+y2__
2 2
Slope
__y1-y2__
x1-x2

if (x1 does NOT = x2)
Fraction Denominatiors
Denominator decreases as Value increases
Algebraic expressions
Factor, Rearrange, Multiply Out

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