Think about what shape the top and bottom will create when each is rotated about its midpoint.
Can you visualize what the resulting solid looks like? It can be a little difficult to sketch 3-D
geometry. You’re probably better off if you can just “see” it in your head. It’ll look something like
this:
In the figure above, the measure of angle QPR is 90 degrees, and the area of triangle PQR is 6. If
triangle PQR is rotated 360º about side PR, what is the total surface area of the resulting solid?