# Area of an Annulus

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)?

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

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## 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.

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## Within our example, the area of the annulus is _______ square units.

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