Modeling with Linear Functions · Exercise 3

Graph and interpret applications of slope–intercept form of a linear function.

Edwin pays a monthly fee for water service on his apartment of $18 plus an additional $0.30 for each HCF (hundred cubic feet) of water used.
ⓐ Write a cost function, C(w), which will give his monthly cost as a function of water used, w, in hundred cubic feet.
ⓑ
\begin{array}{|c|c|}\hline \text{w (in HCF)} & \text{C(w) (in $)} \\ \hline \text{65} & \\ \hline \text{80} & \\ \hline\end{array}

ⓒ On a certain month Edwin’s bill seems high at $50. How many HCF’s of water did Edwin use that month.
ⓓ Graph the function below. Be sure to show the scale you are using.

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Algebra and Trigonometry 2e · §4.2 Modeling with Linear Functions · Exercise 3