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## Glossary of GRE MATH FORMULAS - II

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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 45-45-90 right triangle, the sides are =
X, X, and X square 2
In a 30-60-90 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 =
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