158 Chapter 3 Solving Linear Equations

ERROR ANALYSIS In Exercises 42 and 43, describe the errors.

42. 7(c º 6) = (4 º c)(3) 43. 2(4b º 3) = 8b º 6

7c º 6 = 4 º 3c 8b º 6 = 8b º 6

10c = 10 º6 = º6

c = 1 b = º6

44. CRITICAL THINKING A student

was confused by the results when

solving this equation. Explain what

the result means.

45. COMPUTER TIME A local computer center charges nonmembers $5 per

session to use the media center. If you pay a membership fee of $25, you pay

only $3 per session. Write an equation that can help you decide whether to

become a member. Then solve the equation and interpret the solution.

46. ROCK CLIMBING A rock-climbing gym charges nonmembers $16 per

day to use the gym and $8 per day for equipment rental. Members pay a

yearly fee of $450 for unlimited climbing and $6 per day for equipment

rental. Write and solve an equation to find how many times you must use the

gym to justify becoming a member.

TALL BUILDINGS I

n Exercises 47–49, use the following information.

In designing a tall building, many factors affect the height of each story. How the

space will be used is important. At the Grand Gateway at Xu Hui in Shanghai, the

lowest 7 stories have a combined height of about 126 feet. These stories next to a

shopping mall are unusually tall. The building’s other 43 stories have a more

typical height. If the average height of the other stories had been used for the

lowest 7 stories, then the building could have fit about 3

1

2

more stories.

Source: Callison Architecture. (Actual dimensions have been simplified.)

+ • =

•

47. Explain why you would use

53

2

1

for the “possible number

of stories” in the verbal model.

48. Let h represent the average

height of the other stories.

Finish assigning labels and

write the algebraic model.

49. Solve the equation. Be sure to

simplify the answer. About

how many feet tall are the

stories above the 7th floor?

Average height

of other stories

Possible number

of stories

Average height

of other stories

Number of other

stories

Combined height of

lowest 7 stories

7(y – 2) = –y + 8y – 14

7y

– 14 = 7y – 14

7y = 7y

y = y

ARCHITECT

Designing a building

that is functional, attractive,

safe, and economical

requires teamwork and

many stages of planning.

Most architects use

computers as they write

reports and create plans.

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