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Question
Find the circumference of a circle whose area is 81πcm2.
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Solution
The Area of a Circle with radius r = πr2
Here, Area of a Circle = 81πcm2
⇒ 81π = πr2
⇒ 81 = r2
⇒ r = 9cm
The Circumference of a Circle with radius r = 2πr
The Circumference of a Circle with radius 9
= 2π x 9
= 18πcm.
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