1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3-3)

Solve 7y = 42.

A. 6

B. 7

C.

D.

1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3-3)

A. 8

B. 7

C. –7

D. –8

Solve –8h = 64.

1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3-3)

Solve 24 = 6r.

A. 4

B. 6

C.

D.

1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3-3)

A. 9

B. 5

C. –5

D. –9

The product of a number and 5 is –45. Find the number.

1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3-3)

A. 5 hours

B. 15 hours

C. 20 hours

D. 25 hours

Lynwood earns $7 per hour working at the coffee shop. How many hours does he need to work to earn $105?

1. A

2. B

3. C

4. D0% 0%0%0%

(over Lesson 3-3)

A. 4

B. 5

C. 7

D. 9

Rita invited 16 friends to her birthday party. If she has 112 party favors, how many party favors can each of her friends receive?

Main Idea

Example 1:Problem-Solving Investigation: Work Backward

• Solve problems using the work backward strategy (2.8.8E) (M7.D.2.1).

THINK ABOUT THIS:

List the steps you would take to put your socks and tennis shoes on. STEP 1: Put on my right sock.

STEP 2: Put on my left sock.

STEP 3: Put on my right shoe.

STEP 4: Tie my right shoe

STEP 5: Put on my left shoe.

STEP 6: Tie my left shoe.

• If you were to work backward to take off your socks and shoes, what would be the first steps? List the remaining steps.

• Would it make sense for you to take off your socks before your shoes?

• Would it make a difference if you untied both shoes before taking them off?

• When can the steps of working backward have flexibility and when can they not?

Work Backward

SHOPPING Lucy and Elena went to the mall. Each girl bought a CD for $16.50, a popcorn for $3.50, and a drink for $2.50. Altogether, they had $5.00 left over. How much money did they take to the mall?

Understand You know that the girls have $5 left and the amounts they spent. You need to find the initial amount they had.

Plan Start with the end result and work backward.

Work Backward

Solve They had $5 left.

UNDO the 2 × $2.50 spent on drinks.5

+ 5 = 10

UNDO the 2 × $3.50 spent on popcorn.

10 + 7 = 17

UNDO the 2 × $16.50 spent on CDs.

17 + 33 = 50Answer: So, Lucy and Elena initially had $50.

Work Backward

Check Assume that they started with $50. After buying CD’s, they had $50 – $33 or $17. Then they spent $7 on popcorn; $17 – $7 = $10. Then they spent $5 on drinks; $10 – $5 = $5. So, the answer is correct.

1. A

2. B

3. C

4. D

0% 0%0%0%

A. 11:00 A.M.

B. 11:20 A.M.

C. 11:40 A.M.

D. 12:00 P.M.

AIRPORT Jackson will leave from work to go home before he heads to the airport. He needs to be at the airport at 1:15 P.M. It takes him 45 minutes to drive to the airport from home, 30 minutes to pack at home, and 20 minutes to drive back from work to home. What time should he leave work?

End of the Lesson

Five-Minute Check (over Lesson 3–3)

Image Bank

Math Tools

Solving Equations Using Models

Perimeter

Solving Equations Two-Step Equations