GRE Math

Question 0

0!

Answer 0

1

Question 1

First ten prime numbers

Answer 1

2 3 5 7 11

13 17 19 23 29

Question 2

Percent increase or decrease

Answer 2

% change = delta/initial

then convert to a percent

Question 3

Is 0 even or odd?

Answer 3

Even

Question 4

Interest equation

Answer 4

I = prt

principle * rate * time

Question 5

Work rate equation

Answer 5

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

Question 6

Permutation equation (no repetition)

Answer 6

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

order matters

Question 7

Combination equation

No repetition

Answer 7

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

order doesn’t matter

Question 8

Alternate angles

Answer 8

Inside of Z shape. Aka alternate interior angles.

Question 9

Independent successive choices equation

Answer 9

Just multiply

Question 10

Find the standard deviation (5 steps)

Answer 10

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.

Question 11

Divisibility rules for 3 4 6 9

Answer 11

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

Question 12

x^2 - y^2 =

Answer 12

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

Question 13

(x+y)(x-y) =

Answer 13

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

Question 14

Sum of positive integers from 1 through n

Answer 14

= n(n+1) / 2

Question 15

Numbers to test in quantitative comparisons

Answer 15

0 1 2 -2 1/2

Question 16

Congruent shapes vs. similar shapes

Answer 16

Congruent shapes: same shape, may be rotated

Similar shapes: same shape, may be different size

Question 17

Vertical angles

Answer 17

Opposite each other, and are congruent.

Question 18

Corresponding angles

Answer 18

Are congruent, in same location on two parallel lines.

Question 19

Interior angles

Answer 19

On the same side as the transversal, are supplementary.

Question 20

Complementary angles

Answer 20

Sum = 90

Question 21

Supplementary angles

Answer 21

Sum = 180

Question 22

Area of circle

Answer 22

A = pi * r^2

Question 23

Circumference of circle

Answer 23

C = 2 * pi * r

Question 24

Area of a sector of a circle

Answer 24

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

Question 25

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

Answer 25

1 : 1 : sqrt(2)

Question 26

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

Answer 26

1 : sqrt(3) : 2

Question 27

Area of a parallelogram

Answer 27

A = bh

Question 28

Area of a trapezoid

Answer 28

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

Question 29

Sum of a polygon's interior angles

Answer 29

= 180*(n-2)

Question 30

sqrt(x) * sqrt(y) =

Answer 30

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

Question 31

sqrt(xy) =

Answer 31

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

Question 32

sqrt(x) / sqrt(y) =

Answer 32

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

Question 33

sqrt(x/y) =

Answer 33

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

Question 34

Length of a triangle side compared to the other two sides

Answer 34

Difference of other two < L < sum of other two

Question 35

Distance formula

Answer 35

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

Question 36

Midpoint formula

Answer 36

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

Question 37

Either-or probabilities

Answer 37

Just add (as long as events are independent)

Question 38

Geometric probability

Answer 38

Desired area / total area

Question 39

Definition of standard deviation

Answer 39

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

Question 40

Permutation with repetition formula

Answer 40

P(n,r) = n^r

Question 41

Steps for approaching permutation/combination problems

Answer 41

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

Question 42

Permutations with k indistinguishable objects

Answer 42

P / k! | P / (k! m!)

Question 43

Solving absolute value inequalities | |x|>y

Answer 43

x>y or x<(-y)

Question 44

x^a • x^b =

Answer 44

x^a • x^b = x^(a+b)

Question 45

(x^a)^b =

Answer 45

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

Question 46

(xy)^a =

Answer 46

(xy)^a = x^a • y^a

Question 47

(x/y)^a =

Answer 47

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

Question 48

Solving higher order inequalities | For what values of x is x^2>-6x-5

Answer 48

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.

Question 49

Sqrt(2)

Answer 49

1.4

Question 50

Sqrt(3)

Answer 50

1.7

Question 51

Normal distribution/ bell curve

Answer 51

Within 1 SD: 68% Within 2 SD: 96% (2% 14% 34% 34% 14% 2%)