A circle has circumference 18 pi cm. What is its area in terms of pi?
Answer and explanation
Correct answer: C. 81pi
- Step 1: The circumference is 2 pi r = 18 pi, so r = 9.
- Step 2: The area is pi r^2 = 81 pi.
Answer
81pi.
Why not the others: The radius is half of the circumference divided by pi; using the circumference or the diameter in the area formula gives the other values.
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