Math Showdown: Shells vs. Washers Techniques 

With solids of revolution, your method may depend on what the problem calls for. I start with Shell Method, because everything was given in terms of x. And we were needing to revolve the solid around x=7. But the questions on an exam may say to use the Washer Method, so I show it that way, too.
00:00 - Volumes of Revolution
00:26 - Shells or Washers
00:58 - Shell Method
09:22 - And now Washer Method
20:08 - Quick recap