This document provides examples of using percent proportions to solve problems involving finding percentages, parts, or wholes. It begins with 6 example problems calculating percentages and their answers. It then introduces the percent proportion and shows how to set it up depending on what is being solved for. Several step-by-step examples demonstrate using the proportion to find percentages, parts, and wholes. The document concludes by explaining how percentages can help understand monetary situations and previewing using a percent equation in the next lesson.

1. Course 2, Lesson 2-3
Estimate.
1. 48% of 30
2. 8.5% of 268
3. 112% of 49
4. 83% of 79
5. Twenty-two percent of the seventh-grade class at Santa Ana
Middle School has blue eyes. If the seventh-grade class has 139
students, about how many have blue eyes?
6. Write an estimate of 128% of 179?

2. Course 2, Lesson 2-3
ANSWERS
1. 15
2. 28
3. 55
4. 64
5. 28
6. 225

3. HOW can percent help you understand
situations involving money?
Ratios and Proportional Relationships
Course 2, Lesson 2-3

4. Ratios and Proportional Relationships
Course 2, Lesson 2-3 Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and Council
of Chief State School Officers. All rights reserved.
7.RP.3
Use proportional relationships to solve multistep ratio and percent
problems.
Mathematical Practices
1 Make sense of problems and persevere in solving them.
3 Construct viable arguments and critique the reasoning of others.
4 Model with mathematics.

5. To use the percent proportion to find:
• the Percent
• the Part, or
• the Whole
Ratios and Proportional Relationships
Course 2, Lesson 2-3

6. Percent Proportion
Ratios and Proportional Relationships
Course 2, Lesson 2-3

7. Ratios and Proportional Relationships
Course 2, Lesson 2-3
Find the percent What percent of 5 is 4?
Find the part What number is 80% of 5?
Find the whole 4 is 80% of what number?
4
5
=
100
n
8
5
0p
=
100
4 80
w
=
100
Type Example Proportion

8. 1
Need Another Example?
2
3
4
5
6
Step-by-Step Example
1. What percent of $15 is $9?
Words
Variable
Proportion
What percent of $15 is $9?
Let n represent the percent.
part
whole
percent
Write the proportion.
9 100 = 15 n Find the cross products.
900 = 15n Simplify.
Divide each side by 15.
60 = n
So, $9 is 60% of $15.7

9. Answer
Need Another Example?
What percent of 24 is 18?
75%

10. 1
Need Another Example?
2
3
4
5
6
Step-by-Step Example
What number is 40% of 120?2.
Words
Variable
Proportion
What number is 40% of 120?
Let p represent the part.
part
whole
percent
Write the proportion.
Find the cross products.
Simplify.
p 100 = 120 40
100p = 4,800
Divide each side by 100.
p = 48 So, 48 is 40% of 120.

11. Answer
Need Another Example?
What number is 30% of 150?
45

12. 1
Need Another Example?
2
3
4
5
6
Step-by-Step Example
3. 18 is 25% of what number?
Words
Variable
Proportion
18 is 25% of what number?
Let w represent the percent.
part
whole
percent
Write the proportion.
Find the cross products.
Simplify.
18 100 = w 40
1,800 = 25w
Divide each side by 25.
72 = w So, 18 is 25% of 72.

13. Answer
Need Another Example?
12 is 80% of what number?
15

14. 1
Need Another Example?
2
3
4
5
6
Step-by-Step Example
4. The average adult male Western Lowland
gorilla eats about 33.5 pounds of fruit each
day. How much food does the average adult
male gorilla eat each day?
You know that 33.5 pounds is the
part. You need to find the whole.
Write the proportion.
Find the cross products.
Simplify.
Divide each side by 67.
33.5 100 = w 67
3,350 = 67w
50 = w
The average adult male gorilla eats
50 pounds of food each day.
7

15. Answer
Need Another Example?
Sally read the nutrition facts on a box of her favorite
cereal. Each cup of the cereal provides 7% of the
recommended daily value of potassium. If a cup of
the cereal contains 260 milligrams of potassium,
what is the recommended daily value of potassium?
Round your answer to the nearest whole number.
about 3,714 mg.

16. How did what you learned
today help you answer the
HOW can percent help you understand
situations involving money?
Course 2, Lesson 2-3
Ratios and Proportional Relationships

17. How did what you learned
today help you answer the
HOW can percent help you understand
situations involving money?
Course 2, Lesson 2-3
Ratios and Proportional Relationships
Sample answers:
• You can use the percent proportion to solve situations
involving money.

18. The next lesson will be
about solving problems
using the percent equation.
Predict what the percent
equation might look like
since it is based on the
percent proportion.
Ratios and Proportional RelationshipsRatios and Proportional Relationships
Course 2, Lesson 2-3