A college is planning to construct a retangular parking lot on land bordered on one side by a highway. The plan is to use 680 feet of fencing to fence off the other three sides. What dimensions should the lot have if the enclosed area is to be a maximum?

Answer 1

Let the side parallel to the highway be y ft
let each of the other two sides be x ft
So 2x + y = 680
y = 680-2x

area = xy = x(680-2x) = 680x - 2x^2

which is a parabola opening downwards, and you want its vertex.

Since you are doing this type of question, you must have learned how to find the vertex.
Go for it.