### Home > CALC > Chapter 8 > Lesson 8.1.6 > Problem8-62

8-62.

Will you use Washers or Disks? Will the bounds and integrand be written in terms of x or y?

The outside of this solid will be a cylinder with radius 3.

The inside of the solid will have a hole. But what shape is that hole? Is it cylindrical?

$\text{Or is it determined by }f(y) = \sqrt{(2y)}?$

Notice that the bottom of the hole is cylindrical (with radius 1), while the top of the hole is determined by

$f(y) = \sqrt{(2y)}.$

Consequently, you will need to use the Washer Method twice... both of which are rotated about the y-axis.

Use the eTool below to help solve the problem.
Click on the link to the right to view the full version of the eTool. Calc 8-62 HW eTool