Area = πr² where r represents the radius of the circle
Since we're given the diameter, we divide by 2 to find the radius.
Remember, the radius is just the straight line from the center of a circle to its circumference of (perimeter).
So our radius is 6/2 or 3 cm
Since we're given that the radius of our circle is 3,
we have π(3 cm)² or π(9 cm²) which is written as 9π cm².