Question

How much greater, in square inches, is the area of a circle of radius 20 inches than a circle of diameter 20 inches? Express your answer in terms of pi.

Answer 1

300π in²

Explanation:

The circle with diameter 20 inches has a radius of 10 inches, so an area of ...

A = πr² = π(10 in)² = 100π in²

The circle with a radius of 20 inches has an area of ...

A = πr² = π(20 in)² = 400π in²

The larger circle is larger by ...

(400π in²) -(100π in²) = 300π in²