Formula to find percent

Percent increase=

amount of increase x 100%

original whole         

or

Percent decrease=

amount of decrease x 100%

original whole         

Average=

Sum of terms

Number of terms

How to use AVERAGE to find the SUM?

Sum=

(Average) x (Number of terms)

Formula to find ratio using actual numbers

Ratio=

of

to

Set up a proportion

Ex. The ratio of boys to girls is 3 to 4. If there are 135 boys, how many girls are there?

Answer: 3  =  135

          4        x

3 x x = 4 x 135

x = 180

Probability =

Number of favorable outcomes

               Total number of possible outcomes        

FACTOR Polynomials

ab + ac = a (b+c)

a2 + 2ab + b2 = (a+b)2

a2 - 2ab + b2 = (a-b)2

a2-b2 = (a-b) (a+b)

Area = 1 x (base)(height)

2             

Pythagorean Theorem

a2 + b2 = c2

interest= (principal)x(interest rate)x(time)

interest rate as a decimal

time in years 9 months would = 9

                                             12

final balance=(principal)x(1+interest rate)(time)(c)

                             C

where C= the number of times compounded annually

nPk=   n!

           (n-k)!

where n is(#in the larger group)

and k is (# you're arranging)

nCk=  n!

           k!(n-k)!

where n = # in larger group

and k= # you're choosing

Zero

How do you find the length of an ARC?

arc is a fraction of a circle's circumference

Length of arc = n x 2 pie r

          360

Area of a sector

Sector is a fraction of a circle's area
(think, slice of pie)

Area of sector= n x pie r 2

          360

where n is the degre of the inner angle of the sector

4 pie r2

3