Functions to Linear Models

The Roaming Cell Phone Company charges $15.00 per month plus $0.20 per minute of airtime usage.  If Juanita uses x minutes of airtime, what is an equation that can be used to determine her monthly cell phone bill (C)?

• C = 0.20x + 15

• C =15 (0.20x)

• C = 15 + x + 0.20

• C = 0.20 + 15x

Margaret is a waitress at The Seafood Bonanza.  She earns $3 an hour plus 90% of her tips.  Write an equation for her salary, S, if she works h hours and earns d dollars in tips.

• 3h + 0.90d = S

• S = 90d + 3h

• S = 3d + 90h

• S = 3h + 9.0d

Speedy Boat Rental charges a $15 deposit fee plus $2 for each hour of use to rent a paddle boat.  Write an equation for C, the total cost, to rent the boat for h hours.

• h = 2C + 15

• C = 15h + 2

• h = 15C + 2

• C = 2h + 15

A golf course charges $15 to rent golf clubs and charges $25 per round to play.  Write an equation to represent the total cost, T, for one player.

• T = 15 + 25r

• T = 15g + 25r

• T = 40 r

• T = 15r + 25

A taxi company charges a flat fee of $3 plus $2 per mile driven. Write the function that represents the total cost (C) as a function of the number of miles driven (m). Then, interpret the rate of change and the initial value.

• C(m) = 2m + 3

• C(m) = 3m + 2

• C(m) = 4m + 1

• C(m) = 5m + 2

Bob has $150 in his savings account and saves $40 per month. Which function models his savings?

• y = 150 + 40

• y = 40x + 150

• y = 150x + 40

A man is climbing down from 100 feet high descending 30 feet per minute. Which function models his descent?

• y = 100 - 30x

• y = 100 + 30x

• y = 100x + 30

• y = 100x - 30

Morgan has $263.49 in her bank account.  She babysits two days each week.  Each time she babysits she earns $36.  She deposits all the money she earns into her bank account at the end of the week.  Which linear equation below best models the relationship between the total amount of money in Morgan's bank account(T) and the number of weeks(w) that have passed?

• T = 72w + 263.49

• T = 36w + 263.49

• T = 263.49w + 36

• w = 72T + 263.49

A local donut shop charged $6.50 for a dozen and provided a coupon in the newspaper for $1.50 off an order. Since the donut shop has gained popularity they have changed their coupon which now provides a discount of only half their original coupon's value. What is the equation that represents the value of a customer's order who uses the new coupon with their order?

• y = 6.50x - 0.75

• y = 6.50x + 0.75

• y = 6.50x - 1.50 - 0.75

• y = 5x - 0.75

Heather is a hairdresser and her customers pay $5 to reserve an appointment time and $12 for every hour Heather works on their hair style. As a back to school special she offers to lower her price per hour by $5. What equation represents the total amount paid to Heather, y, after x hours of hair styling?

• y = 5 + 12x

• y = 12x

• y = 7x + 5

• y = 12x + 12