Percentage Basics — Math & Science Lab

By the end of this lesson you will be able to tell what a percent means and find a percent of a number.

%

The Concept Definition

35% = 35 out of 100

Percent Percent means "for every 100." So 35% means 35 out of every 100 equal parts.

Whole The whole is the full group, full price, or full amount.

Part The part is the piece you are finding.

1

The Rule Plain steps

1Change the percent to a fraction out of 100.

2Multiply that fraction by the whole.

3The answer is the part.

Shortcut: 25% means 25/100. That is the same as one fourth.

2

I Do: Snack Vote Example Worked example

A class has 28 students. In a snack vote, 25% chose popcorn. How many students chose popcorn?

25% means 25 out of 100.

Use the direct percent rule: (25 × 28) ÷ 100.

25 × 28 = 700, and 700 ÷ 100 = 7.

Another way: 25% = 0.25, so 28 × 0.25 = 7.

So 7 students chose popcorn.

3

We Do: Move the Percent Guided

40% of 50 = 20

Percent 40%

Use the slider. The grid shows the percent. The answer shows that percent of 50.

40% means 40 out of 100, so 40% of 50 is 20.

4

You Do Practice

1. 50% of 30 = ?

2. 20% of 50 = ?

3. 10% of 90 = ?