# Thread: differentials

1. ## differentials

question:
thickness of each shell is .2cm. Use differentials to approximate the volume of each shell

im looking at a cylinder with
thickness = .2
height = 40
radius = 5cm

volume of cylinder = pi*r^(2)*h

how do i solve this :/ without a change in X given in the equation?

2. I'm sorry, where do you get that there are "200 such shells"? I interpret this problem as related to a single shell with r= 5, h= 40, and dr= .2.

The volume is $\displaystyle 2\pi (5)(40)(.2)$.

3. Originally Posted by HallsofIvy
I'm sorry, where do you get that there are "200 such shells"? I interpret this problem as related to a single shell with r= 5, h= 40, and dr= .2.

The volume is $\displaystyle 2\pi (5)(40)(.2)$.
I also assumed dh=0.2 cm as well so 40cm is 200 annuli (in retrospect it does not seem such a natural interpretation, but should still give the same result).

On second thoughts I don't think it was a sensible attempt at interpreting the question

CB