If the area of a circle is $25\pi$ sq ft, what is its circumference?
A$5\pi$ ft
B$10\pi$ ft
C$25\pi$ ft
D$50\pi$ ft
Answer & Solution
Correct answer: B. $10\pi$ ft
Using $A=\pi r^2$, we get $\pi r^2=25\pi$, so $r=5$ ft. Then the circumference is $C=2\pi r=2\pi(5)=10\pi$ ft.
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