Finding a Percent of a Number

MCC6.RP.3c – Find a percent of a quantity as a rate per 100; solve problems involving finding the whole, given a part and the percent.

Writing a percent as a ratio•Write the percent over 100

Example: Write 15% as a ratio.

15

100

What is a proportion?

A proportion is 2 equal ratios

Using a Proportion to Find the Percent of a Number

Set up a proportion that uses the percent over 100.

Cross multiply to write an equation. Solve the equation.

To set up your proportion, think, “IS over OF equals PERCENT over 100.”

Example – What is 20% of 30?

= 20100

part

whole30x

=100x 30(20)=100x 600

100 100=x 6

Example:

What is 55% of 60?

Find the percent of a number by converting to a decimal.

1. Write the percent as a decimal.

2. Multiply

Example:

What is 35% of 16?

35% converted to a decimal is .35

Multiply .35 x 16

35% of 16 is 5.6