16 Check Your Understanding Homework prep is in your .

Daryl’s Method

If one minute costs 4.5 cents, then a two-minute call will cost 9 cents. Four minutes will cost 18 cents, and eight minutes will cost 36 cents. I need to add the 10 cents. So the total cost is or 46 cents.

Choose a MethodAnother long-distance plan charges 5 cents per call, plus 6 cents for each minute. Find how much a 10-minute call costs with this plan. Describe your method and explain why you chose it.

Standards PracticeStandards Practice AF 1.1

Write an expression for each verbal description.

1. d more than 50

2. 23 times q 3. 5 less than m

4. 7 decreased by b 5. p multiplied by 14

6. f divided by 3 7. the sum of a and 6

8. n less than 19 9. 21 divided by w

36 10cents cents� ,

50 d

50 � d

A long distance call costs 10 cents, plus 4.5 cents for each minute. How much will an 8-minute call cost?

Tina’s Method

I can let m represent the number of minutes. To find the cost of the call, I can use the algebraic expression

I will evaluate the expression for

The telephone call will cost 46 cents.

10 4 5� . .m m � 8.

10 � 4.5m � 10 � 4.5(8)

� 10 � 36

� 46

d Replace m with 8.

d Multiply 4.5 and 8.

d Add 10 to 36.

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Example 1(page 15)

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Chapter 1 Variables and Algebraic Expressions 1-3 Writing Expressions 17

Write an expression for each verbal description.

10. the number of days in w weeks

11. the number of eggs n divided by 9

12. $5 more than the price p

13. 8 lb less than the weight w

14. the number of students s plus 2 teachers

15. $10 multiplied by h hours

16. 175 pages divided by d days

17. Three brothers earn money by doing yard work. The brothers split the money equally. Write an expression that describes how much money each brother earns.

18. Guided Problem Solving A hot-air balloon is at a height of 2,250 ft. It descends 150 ft per min. Find its height after 6, 8, and 10 min.• Make a table to show the pattern of the balloon’s height.• Write an expression for the balloon’s height at m minutes.

Match each expression with its model.

19. 3x 20. 21.

22. Writing in Math Describe a situation you could model with the expression

Customers in a paint store use the table at the right to decide how much paint they need.

23. How much paint do you need to paint an area of 800 ft2?

24. How many square feet can you paint with each gallon of paint?

25. Write an expression for the number of gallons of paint needed for an area of A ft2.

26. How much paint do you need to paint an area of 2,400 ft2?

27. Paint costs $17.95 per gallon. Write an expression to find the cost of the paint needed for an area of A ft2.

7 � �

3

A.

x x

B.

x x x

3 ?

C.

x � 3 3 � x

y � 3.

400800

2,0003,200

1258

Area (ft.²) Gallons

Example 2(page 15)

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Problem Solving