Question

The Watkins family is trying to decide which kind of in-ground pool to install. They are determining whether to put in a saltwater pool or a basic chlorine pool. The graphs below model the average annual cost of owning each type of pool after t years.
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If the family plans to move to their retirement home in 10 years, which pool would be more cost effective to install? How do you know?
The chlorine pool is more cost effective because the y-value at 10 years is less on graph B than it is on graph A.
The saltwater pool is more cost effective because the y-value at 10 years is less on graph A than it is on graph B.
They would be equally cost effective because the vertical asymptotes for each graph are the same.
They would be equally cost effective because the horizontal asymptotes for each graph are the same.

Answer 1

The saltwater pool is more cost effective because the y-value at t = 10 on graph A is less than the y-value at t = 10 on graph B — so its average annual cost after 10 years is lower.