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GRE Math Flashcards

1
Q

Greatest Common Factor

A

1) Divide by common mults
2) Multiply common mults
Use table

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2
Q

Lowest Common Demoninator

A

1) Find GCF
2) Divide either number by GCF
3) Multiply other number by #2

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3
Q

Quadratic Equation

A

ax^2+bx+c=0

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4
Q

Quadratic Formula

A

x = [ -b ± √(b^2 - 4ac)} / 2a

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5
Q

Pythagorean Formula

A

a^2 + b^2 = C^2

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6
Q

Pythagorean Triples

A 
3-4-5
5-12-13
7-24-25
8-15-17
9-40-41
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7
Q

Special Right Triangles

A

45-45-90 :: x-x-x√2

30-60-90 :: x-x√3-2x

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8
Q

Compound Interest

A

Final Balance = Principal * (1 + Rate/Periods)^Time*Periods

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9
Q

Ratio

A

Ratio = of/to

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10
Q

Multiples of 2

A

Last digit divisible by 2

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11
Q

Multiples of 2

A

Digits add up to mult of 3

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12
Q

Multiples of 4

A

Last two digits are mult of 4

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13
Q

Multiples of 5

A

Last digit 0 or 5

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14
Q

Multiples of 6

A

Divisible by 2 and 3

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15
Q

Multiples of 9

A

Digits add to mult of 9

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16
Q

Odd + Odd

A

Even

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17
Q

Odd / Even Rules

A 
O + E = O
O * O = O
O + O = E
E + E = E
E * E = E
O * E = E
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18
Q

First 10 Prime Numbers

A

2, 3, 5, 7, 11, 13, 17, 19, 23, 29

1 not a prime number

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19
Q

Prime Factorization

A

Branch and divide by primes

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20
Q

Bigger or Smaller? (1/2)^2

A

Smaller 1/4

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21
Q

Zeros? 10^6

A

6 zeros: 10^6 = 1,000,000

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22
Q

Bigger or Smaller? (-2)^2

A

Bigger/positive 4

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23
Q

Bigger or Smaller? (-2)^3

A

Smaller/negative -8

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24
Q

Even base to any power? 8^5

A

Even 8^5 = 32,768

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25
Q

Odd base to any power? 5^8

A

Odd 5^8 = 390,625

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26
Q

Mult exponents: 2^2 * 2^3

A

Add: 2^5

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27
Q

Divide exponents: 4^5 / 4^2

A

Subtract: 4^3

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28
Q

Raise exponents: (3^2)^4

A

Mult: 3^8

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29
Q

Fraction exponents: x^0.5

A

Radical: √x

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30
Q

Negative exponents: x^-3

A

Fraction: 1 / x^3

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31
Q

Diff exponent base: x^3 * y^3

A

Mult base: (x * y)^3

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32
Q

Mult radicals: 2√x * 3√y

A

Mult both: 6√(x*y)

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33
Q

Divide radicals: 12√15 / 2√5

A

Div both: 6√3

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34
Q

Mult fractions: 3/4 * 2/3

A

Mult numerator and denominator: 6/12 = 1/2

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35
Q

Div fractions: 4/9 / 4/3

A

Mult by reciprocal: 4/9 * 3/4 = 12/36 = 1/3

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36
Q

Greater fraction? 5/6 or 7/9

A

Cross mult: 5/6 or 7/9 :: 59 = 45 > 67 = 42

37
Q

% Increase

A

Increase / Original x 100%

38
Q

% Decrease

A

Decrease / Original x 100%

39
Q

Part of whole by Percent

A

Part = Percent * Whole

40
Q

Speed Formula

A

Speed = Dist / Time

41
Q

Time Formula

A

Time = Dist / Speed

42
Q

Distance Formula

A

Dist = Speed * Time

43
Q

Avg A per B

A

Total A / Total B

44
Q

Average Formula

A

Avg = Sum of Terms / # of Terms

45
Q

Sum of Terms Formula

A

Sum of Terms = Avg * # of Terms

46
Q

Wtd Avg Formula

A

A(wt1) + B(wt2) = wtd avg

[wts add to 1)

47
Q

Missing Average

A

Sum of Terms + x = Avg * # of Terms

48
Q

Avg of consecutive #s

A

is avg of small and large

49
Q

Unit Conversion

A

Cancel out units

50
Q

Combined Work Formula

A

1/a + 1/b + 1/c = 1/T

[1 job per unit of time T]

51
Q

Solve Inequalities

A

1) Solution is range

2) Mult or Div by negative number must reverse inequality sign

52
Q

Solve for 2 unknowns

A

1) Substitution

2) Combine (add)

53
Q

FOIL

A

x^2 - 3x + 2
+2 : product of missing terms
-3 : sum of missing terms

54
Q

Quadratics: x^2 - y2

A

(x + y) (x - y)

55
Q

Quadratics: x^2 + 2xy + y^2

A

(x + y) (x + y)

56
Q

Quadratics: x^2 - 2xy + y^2

A

(x - y) (x - y)

57
Q

Std Dev Formula

A 
Square root of avg of squared differences to mean
√Avg(differences^2)
1) Diff each value to mean
2) Square diff
3) Avg squared diffs
4) Square root of avg
58
Q

Normal Distribution Std Devs

A 
±1 = 68%
±2 = 95%
±3 = 99.7%
59
Q

Intersection

A

Shared = A ∩ B

60
Q

Union

A

All of both = A U B –> |A U B| = |A| + |B| - |A ∩ B|

61
Q

Exclusive

A

Exclusive union

62
Q

Combination Formula (orderless)

A

n! / k!(n - k)!
n = total number
k = # in each subgroup

63
Q

Permutation Formula (ordered)

A

n! / (n - k)!
Ordered set
n = total number
k = # in each subgroup

64
Q

Probability Formula

A

Prob = # Desired / # Possible

65
Q

Independent Probability Formula

A

P(A) * P(B)

66
Q

Dependent Probability Formula

A

Multiply but calculate P(A) and P(B) as if prior event resulted in success/desired outcome

67
Q

Or Probability Formula (mutually exclusive)

A

P(A or B) = P(A) + P(B)

68
Q

Or Probability Formula (not mutually exclusive)

A

P(A or B) = P(A) + P(B) - P(A and B)

69
Q

Isosceles

A

2 sides, 2 angles

70
Q

Equilateral

A

3 sides, 3 angles

71
Q

Triangle Exterior Angle Sum

72
Q

Triangle Area Formula

A

1/2 * b * h

73
Q

Polygon Sum of Interior Angles

A

Sum interior angles = (n - 2) x 180

74
Q

Trapezoid

A

One pair parallel sides

Area = Avg length of parallel sides * height

75
Q

Parallelogram

A

Two parallel sides

Area = b * h

76
Q

Rhombus

A

Parallelogram w/ 4 equal side lengths

Area = b * h

77
Q

Circle Circumference

78
Q

Circle Area

79
Q

Tangent

A

Line perpendicular to radius

80
Q

π

A

Ratio of circumference to diameter

81
Q

Arc Length

A

Ratio to Circumference equal to arc angle ratio to 360

82
Q

Slope Form

A

y = mx + b

83
Q

Slope Formula

A

y2 - y1 / x2 - x1

84
Q

Perpendicular Lines Slope

A

Negative Reciprocal

85
Q

Volume Cylinder

86
Q

Cylinder Total Surface Area

A

2π4^2 + 2πrh

area of top/bottom + lateral surface area

87
Q

Simple Interest

A

Principal * rate * periods

88
Q

Rate Formula

A

Quantity A / Quantity B

GRE (2 decks)

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