Writing and interpreting functions

A store offers packing and mailing services to customers. The cost of shipping a box is a combination of a flat packing fee of $5 and an amount based on the weight in pounds of the box, $2.25 per pound. Which equation represents the shipping cost as a function of x, the weight in pounds?

• f(x) = 5x + 2.25

• f(x) = 2.25x + 5

• f(x) = 2.25x − 5

Charlie worked for a stone setting company this past summer. He earned $50 for coming to work and an additional $30 every hour for each hour he worked. Formulate a function model Charlie's earnings (e) as a function of the time he worked (t).

In 2003 a gallon of gas cost $1.75. In 2013 a gallon of gas cost $3.50. Write a linear model that represents the cost (x) as a function of the years.

• $f\left(x\right)=1.75x\ +\ 0.175$

• $f\left(x\right)=0.175x+1.75$

• $f\left(x\right)=2013x+3.50$

• $f\left(x\right)=2003x+3.50$

Jerry has $20 and makes $7 per hour. Which function represents the total amount of money Jerry has after working x hours?

• p(x) = 7x + 20

• p(x) = 7 + 20x

• p(x) = 20 + 7

READ THE SIGN VERY CAREFULLY!!! Write an equation for this relationship.

• y=10.99x

• y=22.98x

• y=22x

• y=21.98x

Adrianna has $20 in her savings account. Each week she will add $5 to it. Which equation represents this situation?

• T(w)=25w

• T(w)=20w+5

• T(w)=5w+20

• T(w)=5w

Researchers in Antarctica discovered a warm sea current under a glacier that is causing the glacier to melt. The ice shelf of the glacier had a thickness of approximately 450 m when it was first discovered. The thickness of the ice shelf is decreasing at an average rate of 0.06 m per day.

Which function can be used to find the thickness of the ice shelf in meters x days since the discovery?

• t(x) = 450 - 0.06x

• t(x) = - 0.06(x + 450)

• t(x) = 450 + 0.06x

• t(x) = 0.06 (x + 450)

A cable company charges a monthly fee of $24.50 for cable service. There is an additional monthly fee of $3 for each premium channel. Write a function rule for this.

•  f(x)=24.5+3x
•  f(x)=24.5*3x
•  f(x)=24.5x+3
•  f(x)=24.5x*3

Thomas got a speeding ticket. The cop said he had to pay $10 for each mile per hour he was going over the speed limit. Plus Thomas has to pay $115 court cost. Which equation correctly models what Thomas would have to pay?

• c=10m+115

• c=115m+10

• c=125m

• c=10m-115

Write an equation for this situation.

• y=9.75x
• y=19x
• y=19.25x
• y=9.5x