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Math > GRE Math > Flashcards

GRE Math Flashcards

0
Q

0!

A

1

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1
Q

First ten prime numbers

A

2 3 5 7 11

13 17 19 23 29

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2
Q

Percent increase or decrease

A

% change = delta/initial

then convert to a percent

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3
Q

Is 0 even or odd?

A

Even

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4
Q

Interest equation

A

I = prt

principle * rate * time

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5
Q

Work rate equation

A

1/(rate a) + 1/(rate b) = 1/(rate combined)

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6
Q

Permutation equation (no repetition)

A

P(n,r) = n!/(n-r)!

order matters

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7
Q

Combination equation

No repetition

A

C(n,r) = n!/r!(n-r)!

order doesn’t matter

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8
Q

Alternate angles

A

Inside of Z shape. Aka alternate interior angles.

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9
Q

Independent successive choices equation

A

Just multiply

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10
Q

Find the standard deviation (5 steps)

A
  1. Find the mean.
  2. For each data point, square the difference between the point and the mean.
  3. Find the sum of all step 2s.
  4. Variance = step 3 / number of data points.
  5. Standard deviation = square root of variance.
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11
Q

Divisibility rules for 3 4 6 9

A

3: sum of digits is divisible by 3
4: last two digits is divisible by 4
6: is divisible by 2 and 3
9: sum of digits is divisible by 9

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12
Q

x^2 - y^2 =

A

x^2 - y^2 = (x+y)(x-y)

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13
Q

(x+y)(x-y) =

A

(x+y)(x-y) = x^2 - y^2

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14
Q

Sum of positive integers from 1 through n

A

= n(n+1) / 2

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15
Q

Numbers to test in quantitative comparisons

A

0 1 2 -2 1/2

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16
Q

Congruent shapes vs. similar shapes

A

Congruent shapes: same shape, may be rotated

Similar shapes: same shape, may be different size

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17
Q

Vertical angles

A

Opposite each other, and are congruent.

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18
Q

Corresponding angles

A

Are congruent, in same location on two parallel lines.

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19
Q

Interior angles

A

On the same side as the transversal, are supplementary.

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20
Q

Complementary angles

A

Sum = 90

21
Q

Supplementary angles

A

Sum = 180

22
Q

Area of circle

A

A = pi * r^2

23
Q

Circumference of circle

A

C = 2 * pi * r

24
Q

Area of a sector of a circle

A

A = (sector angle/360) * (A of circle)

25
Q

Ratio of sides in a 45-45-90 isosceles right triangle

A

1 : 1 : sqrt(2)

26
Q

Ratio of sides in a 30-60-90 right triangle

A

1 : sqrt(3) : 2

27
Q

Area of a parallelogram

A

A = bh

28
Q

Area of a trapezoid

A

A = 1/2 * (b1 + b2) * h

29
Q

Sum of a polygon’s interior angles

A

= 180*(n-2)

30
Q

sqrt(x) * sqrt(y) =

A

sqrt(x) * sqrt(y) = sqrt(xy)

31
Q

sqrt(xy) =

A

sqrt(xy) = sqrt(x) * sqrt(y)

32
Q

sqrt(x) / sqrt(y) =

A

sqrt(x) / sqrt(y) = sqrt(x/y)

33
Q

sqrt(x/y) =

A

sqrt(x/y) = sqrt(x) / sqrt(y)

34
Q

Length of a triangle side compared to the other two sides

A

Difference of other two < L < sum of other two

35
Q

Distance formula

A

d = sqrt[ (x-a)^2 + (y-b)^2 ]

36
Q

Midpoint formula

A

M = [ (x+a)/2 , (y+b)/2 ]

37
Q

Either-or probabilities

A

Just add (as long as events are independent)

38
Q

Geometric probability

A

Desired area / total area

39
Q

Definition of standard deviation

A

How much the numbers in a set vary from the set’s mean

40
Q

Permutation with repetition formula

A

P(n,r) = n^r

41
Q

Steps for approaching permutation/combination problems

A
  1. Permutation or combination?
  2. Repetitions allowed?
  3. Indistinguishable objects in base set?
42
Q

Permutations with k indistinguishable objects

A

P / k!

P / (k! m!)

43
Q

Solving absolute value inequalities

|x|>y

A

x>y
or
x<(-y)

44
Q

x^a • x^b =

A

x^a • x^b = x^(a+b)

45
Q

(x^a)^b =

A

(x^a)^b = x^(ab)

46
Q

(xy)^a =

A

(xy)^a = x^a • y^a

47
Q

(x/y)^a =

A

(x/y)^a = (x^a)/(y^a)

48
Q

Solving higher order inequalities

For what values of x is x^2>-6x-5

A
  1. Replace > or < with =
  2. Solve for x. Those are the places on the number line where the expression changes sign.
  3. Test values in those intervals.
  4. Convert this to an inequality.
49
Q

Sqrt(2)

A

1.4

50
Q

Sqrt(3)

A

1.7

51
Q

Normal distribution/ bell curve

A

Within 1 SD: 68%
Within 2 SD: 96%

(2% 14% 34% 34% 14% 2%)

Math (1 decks)

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