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 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 =
- 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