January 21, 2017

Homework Help: Math - Geometry

Posted by Nikki on Wednesday, May 21, 2008 at 8:49pm.

A cylindrical solid has a cylindrical circular hold drilled out of the center. Bascially, it's a circular cylinder with a hollow spot right down the middle. Find the surface area of the resulting solid.

radius of larger circle: 2in
radius of smaller circle (hollow area): 1in
height: 3in

I got this problem wrong on the test, but here's what I did:
I used the formula for the surface area of a cylinder. I found the surface area for the entire cylinder, which was 20pi. Then found the area of the smaller circles, and got 2pi. My resulting answer was 18pi.

Can someone show me where I went wrong? Thanks!

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