Course 2, Lesson 2-5

Use the determine reasonable answers strategy to solve Exercises 1–4.

1. If the speed limit is 65 miles per hour, what is a reasonable amount of time

for the Blackwells to travel 300 miles?

2. There are 400 boys at Oak Middle School and 12% play football. What is a

reasonable number of boys that play football?

3. Suppose you are going to dinner and a movie with a friend. If you spend

$18 and the movie is 62% of the cost, what is a reasonable cost for dinner?

4. Lisa has 6 coins that total $0.86. What are the coins?

5. A number is multiplied by 13. Then 5 is subtracted from the product. The

result is 60. What is the number?

Course 2, Lesson 2-5

ANSWERS

1. 5 hours

2. 50

3. $7.00

4. 3 quarters, 2 nickels, 1 penny

5. 5

HOW can percent help you understand situations involving money?

Ratios and Proportional Relationships

Course 2, Lesson 2-5

Ratios and Proportional Relationships

Course 2, Lesson 2-5 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.3Use proportional relationships to solve multistep ratio and percent problems.

• 7.EE.3Solve multistep 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.

Ratios and Proportional Relationships

Course 2, Lesson 2-5 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.

3 Construct viable arguments and critique the reasoning of others.

4 Model with mathematics.

5 Use appropriate tools strategically.

6 Attend to precision.

•Find percent of change•Find percent error

Ratios and Proportional Relationships

Course 2, Lesson 2-5

Ratios and Proportional Relationships

Course 2, Lesson 2-5

•percent of change•percent of increase•percent of decrease•percent error

Percent of Change

Ratios and Proportional Relationships

Course 2, Lesson 2-5

Words A percent of change is a ratio that compares the change in quantity to the original amount.

Equation percent of change = amount of changeoriginal amount

Percent Error

Ratios and Proportional Relationships

Course 2, Lesson 2-5

Words The is a ratio that compares the inaccuracy of an estimate, or amount of error, to the actual amount.

Equation percent error = amount of erroractual amount

percent error

How did what you learned today help you answer the

HOW can percent help you understand situations involving money?

Course 2, Lesson 2-5

Ratios and Proportional Relationships

How did what you learned today help you answer the

HOW can percent help you understand situations involving money?

Course 2, Lesson 2-5

Ratios and Proportional Relationships

Sample answers:• You can find the percent of change in the in a real-

world situation involving money.• You can find the percent error in the estimated cost of

an item compared to the actual cost.

The next lesson involves solving problems involving sales tax, tips, and markup. How do you think what you learned today will connect

with the next lesson?

Ratios and Proportional Relationships

Ratios and Proportional Relationships

Course 2, Lesson 2-5