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प्रश्न
Find the circumference of the circle whose area is 81π cm 2.
उत्तर
Area = π r2
π r2 = 81 π
r2 = 81
r = 9 cm
circumference = 2 πr
= 2 × π × 9
= 18 π cm
araJmference - 18 π cm
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