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Question
Find the area enclosed between two concentric circles, if their radii are 6 cm and 13 cm respectively.
Solution
Area between two concentric circles = Area of larger cirde - area of smaller circle
Area of the drde = πr2
Radius of bigger drde = r 1 = 13 cm
Radius of smaller drde = r 2 = 6 cm
Required area = `pi "r"1^2 - pi "r"2^2`
`= (22/7 xx 13 xx 13) - (22/7 xx 6 xx 6)`
= 531.1429 - 113.1429
= 418 cm2
Hence, required area = 418 cm2
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