GRE Math Flashcards
Perfect Squares 1-15
1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225
How to recognize if a # is a multiple of 12
The sum of the digits it a multiple of 3 and the last two digits is a multiple of 4. (i.e 144: 1+4+4=9 which is a multiple of 3, and 44 is a multiple of 4, so 144 is a multiple of 12.)
How to recognize a # as a multiple of 9
The sum of the digits is a multiple of 9.
Slope given 2 points
m= (Y1-Y2)/(X1-X2)
How to recognize a multiple of 6
Sum of digits is a multiple of 3 and the last digit is even.
How to recognize a # as a multiple of 4
The last 2 digits are a multiple of 4. (i.e 144 …. 44 is a multiple of 4, so 144 must also be a multiple of 4.)
How to recognize a # as a multiple of 3
The sum of the digits is a multiple of 3
When dividing exponential #s with the same base, you do this to the exponents…
Subtract them.
When multiplying exponential #s with the same base, you do this to the exponents…
Add them.
First 10 prime #s
2, 3, 5, 7, 11, 13, 17, 19, 23, 29
Find distance when given time and rate
d=rt so r= d/t and t=d/r
binomial product of (x+y)(x-y)
x²-y²
factored binomial product of (x+y)²
x²+2xy+y²
factored binomial product of (x-y)²
x²-2xy+y²
binomial product of (x+y)²
(x+y)(x+y)
binomial product of (x-y)²
(x+y)(x-y)
3 What is the relationship between lengths of the sides of a triangle and the measure of the angles of the triangle?
Sides with the same lengths are opposite angles with the same measure.
1 What is an important property of a 30-60-90 triangle?
The triangle is a right triangle.
2 What is an important property of a 30-60-90 triangle?
The hypotenuse is twice the length of the shorter leg.
3 What is an important property of a 30-60-90 triangle?
The ratio of the length of the three sides is x:x√3:2x
The negative exponent x⁻ⁿ is equivalent to what?
1/xⁿ
1 What are the important properties of a 45-45-90 triangle?
The triangle is a right triangle.
2 What are the important properties of a 45-45-90 triangle?
The triangle is isosceles (AC=BC).
3 What are the important properties of a 45-45-90 triangle?
The ratio of the lengths of the three sides is x:x:x√2.
formula for distance problems
distance=rate×time or d=rt
The sum of the angles in a quadrilateral is
360°
The sum of the measures of the n angles in a polygon with n sides
(n-2) x 180
In any polygon, all external angles equal up to
360°
In a Regular Polygon, the measure of each exterior angle
360/n
The consecutive angles in a parallelogram equal
180°
A quadrilateral where two diagonals bisect each other
Parallelogram
In a rectangle, all angles are
Right
Area of a Parallelogram:
A=(base)(height)
(x-y)(x+y)
x²-y²
(x-y)²
x²-2xy+y²
(x+y)²
x²+2xy+y²
An Angle that’s 180°
Straight Angle
The sum of all angles around a point
360°
If a pair of parallel lines is cut by a transversal that’s not perpendicular, the sum of any acute angle and any obtuse angle is
180
Distance
(rate)(time) d=rt
If a lamp increases from $80 to $100, what is the percent increase?
= 25%.
= (actual increase/original amount) x 100%
= 20/80 x 100% = 1/4 x 100% = 25%
The percent decrease of a quantity
= (actual decrease/Original amount) x 100%
If a lamp decreases to $80, from $100, what is the decrease in price?
= (actual decrease/Original amount) x100%
= 20/100x100% = 20%
To increase a number by x%
multiply by 1+x%
To decrease a number by x%
multiply by 1-x%
If a>b then
-a
Probability of an Event
P(E) = number of favorable outcomes/total number of possible outcomes
If Event is impossible
P(E) = ø
Probability of Event all cases
∅≤P(E)≤1
Probability of E not occurring:
1 - P(E)
Circumference of a circle
pi(diameter)
Circumference of a circle
2(pi)r
Area of a circle
(pi)r²
Volume of a rectangular solid
(length)(width)(height)
Vertical lines
Do not have slopes!
Any Horizontal line slope
zero
X is the opposite of
-X
The only number that is equal to its opposite
∅ ∅=∅
7 divided by ∅
Null
∅ Is neither
Positive or Negative
Consecutive integers
x, x+1, x+2
One is (a prime or not?)
NOT A PRIME
Positive integers that have exactly 2 positive divisors are
Prime numbers (2, 3, 5, 7, 11, 13, 17, 19, 23)
∅ Is
EVEN
∅ is a multiple of
zero is a multiple of every number, BUT zero is NOT a FACTOR of any number except zero
∅ is a multiple of
Every number
2 is the only
Even prime number
bⁿ
b∧b∧b (where b is used as a factor n times)
2⁵*2³
2⁸
2⁵/2³
2²
(2²)³
2⁶
2³×7³
(2x7)³
∅²
∅
If a is positive, aⁿ is
Positive
If a is negative and n is even then aⁿ is (positive or negative?)
aⁿ is positive
-3²
9
-3³
-27
If a
a+c
1ⁿ
1
1 is a divisor of
every number
1 is the
smallest positive integer
25^(1/2) or sqrt. 25 =
5 OR -5
What are the real numbers?
All the numbers on the number line (negative, rational, irrational, decimal, integer). All the numbers on the GRE are real. (-2, 1, .25, 1/2, pi)
What are the rational numbers?
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2, 1, .25, 1/2)
What are the irrational numbers?
All real numbers which can’t be expressed as a ratio of two integers, positive and negative (pi, -sqrt3)
What are the integers?
All numbers multiples of 1.
10
11, 13, 17, 19
20
23, 29
30
31, 37
40
41, 43, 47
50
53, 59 note 57=3x19
60
61, 67
70
71, 73, 79