The length of a rectangle is increasing at a rate of 9 cm/s and its width is increasing at a rate of 7 cm/s. When the length is 15 cm and the width is 10 cm, how fast is the area of the rectangle increasing?

Answer 1

A = lw
dA/dt = l dw/dt + w dl/dt
for the given case
dA/dt = 15(9) + 10(7)
= ...