Calculus

Calculus studies how things change. What could be more important than that?

A rectangle with length l and width w has a diagonal of D inches. If the perimeter of the rectangle is 80 inches, express the diagonal of the rectangle in terms of w. Use a lower case w.

The Volume of a cube increases at a constant rate of 10 cm^3 per second. find the rate of change in its total surface area at the instant when its sides are 20 cm long.

How do we solve the question below?

two small towns alpha and beta are on opposite of a main road.