Choose the correct answer of the following question:
Question:

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

Solution:

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).