Page 221 - NUMINO TG_6A

Activity 2 Percent of a Number

jOb ective Find the percent of numbers.

1. Textbook Instructions Activity 2 Percent of a Number

Explain to students how to find a percentage of Learn how to find a percent of a number.
a whole that isn't 100. We use algebraic
methods for this. Method 1 Use a proportion.

Find 25% of 40. a a = 25
Write a proportion. total 40 100

Method 1: Use a proportion. Find a. a 100 = 40 25
Have students write a proportion equal to the a = 10
percent written as a fraction.
1 . Find the percent of a number by using a proportion.

1. Have students find the percent using a a. 25% of 80 b. 20% of 35
proportion.
a 25 a 20
80 = 100 35 = 100

Method 2: Use an Equation. a 100 = 80 25 a 100 = 35 20

Have students set up an equation to find the a = 20 a = 70

missing number, a. Method 2 Use an equation.

Example: Find 18% of 50. Find 18% of 50.
Write a equation.
Step 1: Write an equation. a = 18% of 50

a 18 50 = 18 50
100 100

Step 2: Find a. Find a. =9

a9

2. Have students find the percent using an 2 . Find the percent of a number by using an equation.
equation.
a. 60% of 70 b. 4% of 125

Ask students which method they prefer and a = 60 70 a= 4 125
why. 100 100

a = 42 a= 5

124

2. Build Understanding

Explaining the methods in detail will help students understand what is going on. With Method 2, when being
asked x% of a, you can always rewrite this as x% a. Then, pick your preferred way to display the percent
and quickly solve the problem.

204 NUMINO Teacher s Guide