Question

The width of a rectangle increases at 2 cm/s, while the length decreases at 3cm/s. How fast is the area of the rectangle changing when the width equals 20 cm and the length equals 50cm?

Answer 1

A = l*w

dA = l dw + w dl dw = 2 ; dl = -3

Answer 2

dA = 50(2) + 20(-3)

dA = 100 -60 = 40 cm^2 / sec

Answer 3

a square is the biggest area, so until it reaches that point, it increases i think