Math 6A (Periods 1 & 2)

Working With Percents

Review: When changing a percent to a fraction we use the following proportion:

 

3.5% = 3.5/100 = 35/1000 = 7/200

Looking at

What percent of 225 is 90?  When setting up an equation we get

225n = 90

However we can use a similar proportion to  

 to solve any percent problem!

The fraction a/b really represents the part/ whole

  Or easier stated:

Looking at the above problem we have

Of course we simplify as much as possible before we cross multiply

we get n = 10(4) = 40

so the solution is 40%

EXAMPLE: 

45% of 600 is what number?

Now this simplifies really easily

and we just have

n = 6(45)

n = 270

The number is 270.

EXAMPLE: 

96% of 85 is what number?

Again, this simplifies to

With cross products we get

5n = 24(17)

5n = 408

Divide both sides by 5

5n/5 = 408/5

n = 81.6

81.6 is our solutions

EXAMPLE: 

What number is 76% of 350?

When you simplify  x= 38(7)
x = 266
EXAMPLE: 

56 is 4% of what numbers?

Definitely simplify and you get

x = 25(56)

x = 1400