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प्रश्न
Find the surface area of a sphere of diameter 21 cm .
उत्तर
Diameter = 21cm
Radius - `"diameter "/ 2 - 21/2 - 10.5cm`
∴Surface area - `4πr^2 - 4π × (10.5)^2 - 4 × 22/7 × 10.5^2 - 1386 cm^2`
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