GRE MATH FORMULAS  II
Terms
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 Factor or Divisor =
 Any integer that leaves no remainder (i.e a reaminder of 0) when it is dvided into another integer:1, 2, 5, 10 are the factors (or divisors) of 10
 Prime Number
 A positive integer that has exactly two divisors. The first few primes are 2, 3, 5, 7, 11, 13, 17 (not 1)

bm bn
b raise to m, b raise to n = 
bm
 = (m n)
bn b 
m n
(b )
= 
mn
b 
2
(squ a) =  sq a * sq a
 To compare two fractions
 convert them to decimals by dividing the numerator by the denominator
 To multiply two fractions,

Multiply their numberator and multiply their denominators
3/5 * 4/7 = 3*4/5*7 = 12/35  To divide any number by a fraction

Multiply that number by the reciprocal of the fraction
3/5 divided by 2/3 = 3/5* 3/2 = 9/10  To add or subtract fraction with different denominators, f

first rewrite the fraction as equivalent fractions with the same denominator:
1/6+3/4 = 2/12 + 9/12 = 11/12  Percent increase of qty =

Actual increase
 * 100%
Original amount  Percent decrease of qty =

Atcual decrease
 * 100%
Original amount  Ratio of 2 to 3 =
 2/3 or 2:3

Average of set of n numbers
= 
Sum of the numbers

n  Probability =

Favorable Outcomes

Total Possible Outcomes 
Percent Formula
Part =  Percent * Whole
 The 3 exterior angles of a triangle add up to
 360 degrees
 In any triangle, the sume of the measure os the three angles is

180 degrees
x+y+z = 180 
In any triangle
1) The longest side  = is the opposite the largest angle
 2) the shortest side
 = is the opposite the smallest angle
 3)Sides with the same length
 = Are opposite angles with the same measure
 In a 454590 right triangle, the sides are =
 X, X, and X square 2
 In a 306090 right triangles, the sides are =
 X, X Square 3 and 2X
 Area of Right trinagle =
 1/2 * base * height
 Area of an equilateral triangle with equal sides =

2
S * Square 3

4  In any quadrilateral, the sume of the measures of the four angles
 = 360 degrees

For Parallelogram
Area =  Base * Height
 Perimeter of Pallelogram =
 2(a + b)
 Area of Rectangele =
 Length * Width
 Perimeter of Rectangel =
 2(L + W)
 Area of a Square =

2
S  Area of a square can also be =

1 2
 d
2  Perimeter of a square =
 4s (s = sides)
 Diameter of a circle =
 2* radiuis
 Circumference of a Cirle =
 PI * D = 2 PI R
 Area of a circle =

2
PI r  Length of an Arc
 (n/360) * (2PI r)
 Area of a sector, if n is the degree measure of the sector's central angle =

2)
(n/360) * (PI r
PI * R square  Surface Area of Rectangular =
 2(LW +LH + WH)= 2LW +LH +2 WH
 Suface Area of cube =

6e square
6 * e square  Volume of a cylider =
 PI * R square * height
 Surface of a cylinder =
 2PI r h
 Volume of a Rectangular solid =
 L * W * H
 Volume of a cube =

3
L * L * L = L  Average speed =

Total Distance

Total time  Average A per B =

Total A

Total B 
Probability formula
Probability = 
Number of Favorable Outcome/
Total no. of Possible Outcomes  If E is impossible, then P(E) =
 0
 If it is certain that E will occur, then P(E)=
 1
 In all other cases
 0 <P(E)<1
 The probability that the even E will not occur =
 1 P(E)
 Counting principle: if two jobs need tobe completed and there are m ways to do the first job and n ways to the second job, then there are
 m * n ways to do one job followed by th eother