Question

The length of a rectangle is increasing at a rate of 10 cm/s and its width is increasing at a rate of 6 cm/s. When the length is 12 cm and the width is 10 cm, how fast is the area of the rectangle increasing?

Found the answer. It is 172square cm/sec

now need to find

How fast is the perimeter of the rectangle increasing?

Answer 1

let the length be l, width w
l = 10 ----> l' = 12
w = 6 ---> w' = 10
if A = lw
then, A' = l'*w + l*w'
A' = 12 * 6 + 10 * 10 = 72 + 100 = 172

Answer 2

Yeah i found 172 need to find how fast is the PERIMETER of the rectangle increasing