(7) Lesson 2.4

1. Course 2, Lesson 2-4
Find each number. Round to the nearest tenth if necessary.
1. What percent of 80 is 25?
2. What number is 30% of 80?
3. 30 is 40% of what number?
4. $6 is what percent of $42?
5. What number is 0.2% of 4?
6. Joseph saves 30% of his allowance each week. If he saves $24
in 5 weeks, how much allowance does Joseph receive each
week?

2. Course 2, Lesson 2-4
ANSWERS
1. 31.3%
2. 24
3. 75
4. 14.3%
5. 0.008
6. $16

3. HOW can percent help you understand
situations involving money?
Ratios and Proportional Relationships
Course 2, Lesson 2-4

4. Ratios and Proportional Relationships
Course 2, Lesson 2-4 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.2
Recognize and represent proportional relationships between quantities.
• 7.RP.2c
Represent proportional relationships by equations.
• 7.RP.3
Use proportional relationships to solve multistep ratio and percent
problems.
• 7.EE.3
Solve multi-step real-life and mathematical problems posed with positive
and negative rational numbers in any form (whole numbers, fractions, and
decimals), using tools strategically. Apply properties of operations to
calculate with numbers in any form; convert between forms as appropriate;
and assess the reasonableness of answers using mental computation and
estimation strategies.

5. Ratios and Proportional Relationships
Course 2, Lesson 2-4 Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and Council
of Chief State School Officers. All rights reserved.
Mathematical Practices
1 Make sense of problems and persevere in solving them.
2 Reason abstractly and quantitatively.
3 Construct viable arguments and critique the reasoning of others.
4 Model with mathematics.

6. To use the percent equation to find:
• the Percent
• the Part, or
• the Whole
Ratios and Proportional Relationships
Course 2, Lesson 2-4

7. Percent Equation
Ratios and Proportional Relationships
Course 2, Lesson 2-4

8. Ratios and Proportional Relationships
Course 2, Lesson 2-4
Type Example Proportion
Find the Percent 3 is what percent of 6? 3 = n 6
Find the Part What number is 50% of 6 p = 0.5 6
Find the Whole 3 is 50% of what number? 3 = 0.5 w




9. 1
Need Another Example?
2
3
4
5
6
Step-by-Step Example
1. What number is 12% of 150?
Do you need to find the percent, part, or whole? part
0.01 150 = 15Estimate
Write the percent equation. 12% = 0.12p = 0.12 150
part = percent whole
p = 18 Multiply.
So, 18 is 12% of 150.
18 is close to the estimate of 15. So, the answer is reasonable.
You can also check your answer using the percent proportion.
Check7
18 100 = 150 12
1,800 = 1,800
?

10. Answer
Need Another Example?
What number is 46% of 200?
92

11. 1
Need Another Example?
2
3
4
5
6
Step-by-Step Example
2. 21 is what percent of 40?
Do you need to find the percent, part, or whole? percent
Estimate
Write the percent equation.21= n 40
part = percent whole
Divide each side by 40.
0.525 = n
So, 21 is 52.5% of 40.
Check
Simplify.
7 52.5% 50%

12. Answer
Need Another Example?
26 is what percent of 32?
81.25%

13. 1
Need Another Example?
2
3
4
5
6
Step-by-Step Example
3. 13 is 26% of what number?
Do you need to find the percent, part, or whole? whole
Estimate
Write the percent equation. 26% = 0.2613 = 0.26 w
Divide each side by 0.26.
50 = w
So, 13 is 26% of 50.
Check
Simplify.
7
of 48 = 12
part = percent whole

14. Answer
Need Another Example?
12 is 40% of what number?
30

15. 1
Need Another Example?
2
3
4
5
Step-by-Step Example
4. A survey found that 25% of people aged 18-24 gave up their home
phone and only use a cell phone. If 3,264 people only use a cell
phone, how many people were surveyed?
Words
Variable
Equation
3,264 people is 25% of what number of
people?
Let w represent the number of people.
3,264 = 0.25 w
3,264 = 0.25 w Write the percent equation. 25% = 0.25
Divide each side by 0.25. Use a calculator.
Simplify.13,056 = w
About 13,056 people were surveyed.

16. Answer
Need Another Example?
A survey found that 36% of people preferred
comedies over action movies. If 450 people
prefer comedies, how many people were
surveyed?
1,250 people

17. How did what you learned
today help you answer the
HOW can percent help you understand
situations involving money?
Course 2, Lesson 2-4
Ratios and Proportional Relationships

18. How did what you learned
today help you answer the
HOW can percent help you understand
situations involving money?
Course 2, Lesson 2-4
Ratios and Proportional Relationships
Sample answers:
• The percent equation can be used to solve situations
involving money.

19. Write a real-world problem
involving percent that can
be solved by using the
percent equation. Be sure
to include two of the three
elements needed to solve the
problem (part, percent, whole).
Ratios and Proportional RelationshipsRatios and Proportional Relationships
Course 2, Lesson 2-4