Question

The water company has a different monthly pricing plan for residential customers than for business customers. For each pricing plan, cost in dollars) dependson water used in hundreds of cubic feet, HCF), as shown below.(a) If the monthly water usage is 18 HCF, which plan costs less?Residential Plan/Business PlanHow much less does it cost than the other plan?(b) For what amount of monthly water usage do the plans cost the same?If the monthly water usage is more than this amount, which plan costs less?

Answer 1

In order to answer the question, we need to refer to the image provided with the two different plans:

Question a) In order to decide which plan costs less for 18 HCF , we go on the horizontal axis to the mark 18 and read tha values for the red line(Residential) versus the blue line (Business)

We read $36 for the residential and $32 for the business, so the business costs less than the residential , and the difference is 4 dollars.

Question b) The plans cost the same at the point where the two lines intersect. That is for HCF = 14 and which shows $28 dollars.

Then, if the monthly water usage is MORE (that means we move to the right of that intersection point for larger values of the horizontal variable HCF), then the RED line becomes on top of the blue one, meaning that the cost in dollars for the red line will be LARGER that the blue one. The answer for this part is therefore that: If the monthly uses goes above this 14 HCF, the business plan costs less.