Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GRE > Math Formulas and Concepts > Flashcards

Math Formulas and Concepts Flashcards

You may prefer our related Brainscape-certified flashcards:
GRE® Vocabulary flashcards GRE® Psychology flashcards
1
Q

Special right triangle ratios

A

3:4:5 and 5:12:13

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Equilateral triangle

A

Equal side, 60-60-60 degree

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Isosceles triangle

A

2 equal sides corresponding to 2 equal angles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Special right triangle angles

A

45-45-90 1:1:sq. rt. 2; 30-60-90 1:sq. rt. 3:2 half an equilateral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Find common factor of 2 #’s

A

Find prime factors and all combinations of shared prime factors.

Ex: What factors do 135 & 225 have in common?
135=3335
225=3355
335 so 3, 5, 9, 15, 45

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Find least common multiple (LCM)

A

Find prime factorization and determine the greatest number of times each factor is used between the two numbers.

Ex: LCM of 28 & 42?
28 = 227, 42 = 237
LCM = 223*7=84

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Use average to find sum of terms

A

Sum = average x # of terms

Ex: 17.5 is the average of 24 #’s. What’s the sum of the terms?
Sum=17.5*24=420

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Find average of evenly spaced #’s

A

Equal to the average of the smallest and largest #’s.

Ex: what’s the average of all the integers from 13 to 77?
(13+77)/2=90/2=45

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Counting consecutive #’s

A

of integers from A to B inclusive is B-A+1

Ex: how many integers are there from 73 to 419 inclusive?
419-73+1 = 347

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Solve an inequality

A

When multiplying or dividing by a negative, REVERSE THE INEQUALITY SIGN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Absolute values

A

Ex: If |x-3|<2 what is the range of possible values for x?

if |x-3|<2 then x-3<2 and x-3>-2, so x<5 and x>1, thus 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Circumference of a circle

A

C=2rpi=d*pi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Area of a circle

A

A=pi*r^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Determine combined % up or down

A

Start with 100 as a value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Solve a compound interest problem

A

Final balance = principal(1+(interest rate/C))^(timeC) where C= # of times compounded annually

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Remainders problem

A

Pick a number that fits the given conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Combines work problem

A

(1/r)+(1/s)=(1/t) where r, s = different people’s work times and t = combined work time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Dilution/mixture problem

A

(% difference between weaker and desired)(amount of weaker)=(% difference between stronger and desired)(amount of stronger)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Group problem with both/neither

A

group1+group2+neither-both=total

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Standard deviation

A
  1. Find average of set
  2. Find difference between mean and each value
  3. Square each difference
  4. Find average of squared differences
  5. Take the square root of average
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Multiply/divide with exponents

A

(x^a)*(x^b)=x^(a+b)

x^c)/(x^d)=x^(c-d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Exponent to exponent

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Bases with exponent 0

A

x^0=1 except 0^0 is undefined

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Fractional exponents

A

x^(a/b)=b*sq. rt (x^a)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Find max/min lengths for a side of a triangle

A

If a, b are two sides of a triangle, then |a-b|

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Angles of a regular polygon (all angles =)

A

Sum of interior angles in polygon with n sides = (n-2)*180

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Length of arc

A

length of arc=(n/360)2r*pi where n=interior angle

28
Q

Area of sector of a circle

A

Area of sector=(n/360)pir^2 where n=interior angle

29
Q

Surface area of rectangle solid

A

Surface area=2lw+2wh+2lh

30
Q

Volume of a cylinder

A

volume = area of baseheight=hpi*r^2

31
Q

Surface area of cylinder

A

surface area = 2pir^2 + 2hr*pi

32
Q

Digit

A

Number that makes up another number

33
Q

Number

A

One or a combination of digits

34
Q

Integer

A

Numbers that have no fractional part

35
Q

Properties of Zero

A
  • even
  • added to any number equals that number
  • multiplied by any number equals 0
  • cannot divide by 0
36
Q

Properties of adding even/odd numbers

A

Even + even = even
Odd + odd = even
Even + odd = odd

37
Q

Properties of multiplying even/odd numbers

A

Eveneven=even
Oddodd=odd
Even*odd=even

38
Q

Consecutive integers

A

Integers listed in order of value without any missing integers between them

39
Q

Absolute value

A

The distance from 0 to a number on the number line

40
Q

Factor

A

A number that will divide evenly into another integer

41
Q

Multiples

A

All the integers for which a number is a factor

42
Q

Prime number

A

An integer with only two factors, itself and one. Starts with 2.

43
Q

Divisibility tricks for each digit

A
  • # divisible by 3 if sum of digits is divisible by 3
  • # divisible by 4 if last two digits form a number divisible by 4
  • # divisible by 5 if units digit is 0 or 5
  • # divisible by 6 if divisible by both 2 and 3
  • # divisible by 8 if last 3 digits form a number that’s divisible by 8
  • # divisible by 9 if sum of digits is divisible by 9
44
Q

Remainder

A

An integer left over when one number is not evenly divisible by another

45
Q

Sum

A

The result of addition

46
Q

Difference

A

The result of subtraction

47
Q

Product

A

The result of multiplication

48
Q

Quotient

A

The result of division

49
Q

Divisor

A

The number you divide by

50
Q

Numerator

A

The top number of a fraction

51
Q

Denominator

A

The bottom number of a fraction

52
Q

Terms

A

The numbers and expressions used in an equation

53
Q

Order of operations

A

PEMDAS or parenthesis, exponents, multiplication, division, addition, subtraction

Multiplication and division as well as addition and subtraction are done in the same step going from left to right.

54
Q

Properties of multiplying Positive/negative

A

Positivepositive=positive
Negativenegative=positive
Positive*negative=negative

55
Q

Properties of dividing positive/negative numbers

A

Positive/positive=positive
Negative/negative=positive
Positive/negative OR negative/positive=negative

56
Q

Fraction

A

Expresses the number of parts out of a whole. Consists of a integer numerator on top and an integer denominator on bottom.

57
Q

Adding/subtracting fractions

A
  • if common denominator exists just add or subtract numerator and put the result over the denominator
  • if there are different denominators, first find a common denominator. This entails finding a common multiple of both denominators and multiplying the numerator and denominator of each fraction by the respective factors of the multiple. Then proceed as above.
58
Q

Multiplying fractions

A

Multiply numerators and then denominators together and reduce the resulting fraction

59
Q

Dividing fractions

A

Flip the second fraction such that denominator is the numerator and the numerator is the denominator and then multiply the two resulting fractions.

60
Q

Mixed number

A

A number that is represented as an integer and a fraction. Ex: 2 and 2/3

  • convert to a fraction by multiplying the denominator by the integer and adding the numerator and putting the result over the denominator.
61
Q

Decimal

A

A different form of expressing a fraction

62
Q

Percentage

A

Type of fraction that always has 100 as the denominator

63
Q

Percent increase/decrease

A

Percent change=(difference/original)*100 where difference is the lesser number is subtracted from the greater.

64
Q

When to use Plug-in-a-number

A

When there are variables in the problem and answer choices.

*Note: in quantitative comparison questions, plug in multiple times using Fractions, Repeats, One, Zero, Extremes, or Negatives to eliminate all answer choices.

65
Q

When to use Plug-in-the-answer

A
  1. If the problem has the phrase “how much…”, “how many…”, or “what is the value of…”.
  2. Specific numbers in the answer choices in ascending or descending order.
  3. If you’re tempted to write your own algebraic formulas

*Note: start with answer choice C to do half the work.

66
Q

Standard deviation percentages
0-1 SD = ?
1-2 SD = ?
2+ SD = ?

A

0-1 SD = 34%
1-2 SD = 14%
2+ SD = 2%

GRE (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions