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39 Cards in this Set
 Front
 Back
Multiples of 2

Last digit is even


Multiples of 3

Sum of digits is a multiple of 3


Multiples of 4

Last two digits are a multiple of 4


Multiples of 5

Last digit is 5 or 0


Multiples of 6

sum of digits is a multiple of 3 and lest digit is even


Multiples of 9

Sum of digits is a multiple of 9


Multiples of 10

Last digit is 0


Multiples of 12

Sum of digits is a multiple of 3, Last 2 digits are a multiple of 4


Isosceles Triangle

Two equal sides, two equal angles


Equilateral Triangle

3 equal sides, 3 60 degree angles


Order of operations

PEMDAS: Parentheses, exponent, multiply, divide, addition, subtract


Factoring Polynomials

Classics:
ab+ac = a(b+c) a<2>+2ab+b<2> = (a+b)<2> a<2>2ab+b<2> = (ab)<2> a<2>b<2> = (ab)(a+b) 

Simplify polynomials

Multiply to eliminate parentheses & combine like terms:
(3x<2>+5x)(x1) 3x<2>(x1) +5x(x1) 3x<3>3x<2>+5x<2>5x 3x<3>+2x<2>5x 

Actual number from a ratio

Set up a proportion:
Ratio of Boys to Girls is 3 to 4 If there are 135 boys, how many girls are there? 3/4 = 135/x 3x=4(135) x=180 

Ratio

OF on top, TO on bottom
OF/TO Ratio of 20 oranges to 12 apples 20/12 or 5/3 

Average of consecutive numbers

The average of the sum of the largest and the smallest numbers:
Average all consecutive integers from 13 to 77 13+77 = 90 90/2 = 45 

Count consecutive numbers

Integerts from A to B inclusive is BA+1:
73 to 419 inclusive 41973+1 = 347 

Sum of consecutive numbers

Sum = (average)x(no. of terms):
Sum of integers 10 to 50 inclusive Average  (10+50)/2 = 30 No. of terms  (5010)+1=41 Sum = 30x41 = 1,230 

Sum of consecutive numbers from Average

Sum = (average) x (no. of terms):
17.5 is the average of 24 terms the sum is 17.5x24 = 240 

Common multiples

Common multiple is the product.
Least common multiple comes from dividing the product by common factors: 28 and 42 28x42=1,176 (28=2x2x7 42=2x3x7) 1,176/2 = 588.58/7 = 84 

Common factors

Break down to prime factors.
Multiply shared prime factors in every possible combination: 135 and 225 135 = 3x3x3x5 225=3x3x5x5 3x3 = 9 3x5=15 3x3x5=45 

Decimals to fractions

use the place:
.25 = 25/100 = 1/4 .5  5/10 = 1/2 

Fractions to decimals

use division
3/5 = 3.0/5 = .6 

similar triangles

proportional triangles, all angles are equal, sides may be different


pythagorean theorum

a<2> + b<2> = c<2>


area of a triange

bh/2


area of a parallelogram

bh


area of a trapezoid

average of sides x h


special right triangles

345 & 51213 = 90
306090 = 1, sq.rt. of 3, & 2 (hypotenuse) 454590 = 1, 1 & sq.rt. of 2 (hypotenuse) 

area of a circle

pi r <2>


circumference of a circle

2 pi r


slope of a line

rise/run = delta y/delta x


multiply + divide

product + quotient


counting possibilities

be systematic


calculate a probability

probability =
number of favorable outcomes / total possible outcomes 

determine a rate

maintain units
words / minute 

range

number that appears most often


mode

positive difference between highest and lowest value


median

place in order + use middle number
two middle numbers, use average 