Question

Suppose that a household's monthly water bill (in dollars) is a linear function of the amount of water the household uses (in hundreds of cubic feet, HCF). Whengraphed, the function gives a line with a slope of 1.35. See the figure below.If the monthly cost for 24 HCF is $49.88, what is the monthly cost for 28 HCF?

Answer 1

1) Gathering the data:

slope: m= 1.35

24 HCF -----> 49.88

28 HCF ----> ?

2) Since we have the slope we can plug it into the point-slope formula:

`\begin{gathered} (y-y_1)=m(x-x_1) \\ (28-24)=1.35(49.88-x_1) \\ \\ (4)/(1.35)=(1.35(49.88-x_1))/(1.35) \\ 2.96=49.88-x_1 \\ 2.96-49.88=-x_1 \\ -46.92=-x_1 \\ x_1=46.92 \end{gathered}`

Note that we've used the point-slope formula and then plugged it into that so that we could find the first x-coordinate. Considering (49.88, 24) and (46.92, 28) the points.

3) Hence, the answer is $46.92