If the surface area of sphere is 154 cm , then its radius in cms.
If the surface area of sphere is 154 cm , then its radius in cms.
A) 7
B) 14
C) 21
D) 7/2
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Correct option is (D) \(\frac{7}{2}\)
Let radius of the sphere is r cm.
\(\therefore\) \(4\pi r^2\) = 154 \((\because\) Surface area of sphere \(=4\pi r^2)\)
\(r^2=\frac{154}{4\pi}=\frac{154\times7}{4\times22}=\frac{7\times7}4=\frac{7^2}{2^2}=(\frac72)^2\)
\(\therefore\) \(r=\frac72\)
Hence, radius of sphere is \(\frac72\,cm\)
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