- #1

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## Homework Statement

http://imgur.com/VzZjSEH

I took a screen shot so I did not leave anything out.

## Homework Equations

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 r

^{2}- inner r

^{2}).

So he did -657 * pi * (.042

^{2}- .026

^{2})

Can someone explain to me how this is right?