The length of a rectangle is increasing at a rate of 7 centimeters per second and its width is increasing at a rate of 1 centimeters per second.

Question

When the length is 20 cm and the width is 15 centimeters, how fast is the area of the rectangle increasing?

Rate of change for area: ______ square centimeters per second

Answer 1

Area A = lw; dA/dt = wdl/dt + ldw/dt = 15cm·7cm/s + 20cm·1cm/s = 125 cm²/s