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 .
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?