I took a screen shot so I did not leave anything out.
Surface area, and volume of a sphere.
The Attempt at a Solution
I am trying to find the linear charge density from the charge volume density. I got it explained from a friend. It was right, but made no sense. He did it by taking the volume density, and multiplying it by the charge volume density by pi, and (outer r2 - inner r2).
So he did -657 * pi * (.0422 - .0262)
Can someone explain to me how this is right?