Determine Functions and Linear Functions

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

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

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

Randy charges his tenants $400 each month to rent his houses plus $600 security deposit. In the new year, the property taxes increased on the area where he rents so as a result he must increase the rate of change by $25 to ensure his profits are not harmed. What equation best represents how much his tenants will now have to pay?

• y = 425x + 600

• y = 425 + 600x

• y = 400x + 625

• y = 400 + 625x

Michelle and her husband want to go skydiving! The equation, f(x) = 12000 - 125x, represents the height (in feet) of the skydivers, f(x), after x seconds of falling. Michelle and her husband are adrenaline junkies so they have asked to increase the starting jump height by 500 feet and will deploy their parachute late which will change their falling speed to 200 feet per second. What equation represents these changes?

• y = 12000 - 200x

• y = 12500 + 75x

• y = 12500 - 200x

• y = 12200 - 625x