# Area of an Annulus

- Author:
- WheelerELHS, David McBain

- Topic:
- Area

## Definition of Annulus of a Circle

An

**annulus of a circle**is the region between two concentric circles. Recall, concentric circles are circles that have the same center. Move the "outer" point until the large radius is 5 units. Move the "inner" point until the small radius is 3 units.## In terms of pi, what is the area of the "outer circle" (r = 5 units)?

## In terms of pi, what is the area of the "inner circle" (r = 3 units)?

## Since we can find the area of the "outer circle" and "inner circle", we can easily find the area of the annulus too.

The **area of the annulus** is simply the area of the ___________ circle subtracted by the area of the ____________ circle.