a rectangle R of length l and width w is revolved around the line L. Find volume of resulting solid of revolution.
The theorem of Pappus may be a cool way to go with this one.
Find the centroid of the rectangle. Rectangles are easy for that. It is in the center.
Find the distance the center of the rectangle is from what it is being revolved around. It's area is merely lw.
Volume would then be