- #1

QuarkCharmer

- 1,051

- 3

## Homework Statement

Stewart Calculus 6E, 3.8 #4

4.) The length of a rectangle is increasing at a rate of 8cm/s and its width is increasing at a rate of 3cm/s. When the length is 20cm and the width is 10cm, how fast is the area of the rectangle increasing?

## Homework Equations

A = LW

## The Attempt at a Solution

I am not entirely sure how to set this problem up. I think I would start with A=LW, and then implicitly differentiate to:

[tex]A' = L'W + W'L[/tex]

Then perhaps, plug in my values for the change in length and width as so:

[tex]A' = 8W + 3L[/tex]

But that doesn't seem right?