63.585 inches^2
Explanation:
The formula for the area of a circle is...
We need the radius for this, but we have the diameter. Since radius is half of the diameter, we know the radius will be 4.5. We can plug that in.
Answer: 63.61725124
area = pi x r^2
diameter is double the radius, labeled r in the formula.
9/2 = 4.5
r = 4.5
area = pi x 4.5^2
area = 63.61725124 or 81/4pi
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