Choose the correct answer of the following question:
If the surface area of a sphere is 616 cm2, its diameter (in cm) is
(a) 7 (b) 14 (c) 28 (d) 56
Let the radius of the sphere be $r$.
As,
Surface area of the sphere $=616 \mathrm{~cm}^{2}$
$\Rightarrow 4 \pi r^{2}=616$
$\Rightarrow 4 \times \frac{22}{7} \times r^{2}=616$
$\Rightarrow r^{2}=\frac{616 \times 7}{4 \times 22}$
$\Rightarrow r^{2}=49$
$\Rightarrow r=\sqrt{49}$
$\Rightarrow r=7 \mathrm{~cm}$
$\therefore$ Diameter of the sphere $=2 r=2 \times 7=14 \mathrm{~cm}$
Hence, the correct answer is option (b).
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