Find the surface area (in $$cm^2$$​) of a sphere whose diameter is 21 cm.

Correct option is B

Given:

Diameter of the sphere (d) = 21 cm

Formula Used:

Radius of the sphere (r) = $$\frac{d}{2}$$​​

Surface area of a sphere = 4πr²

Solution:

r =$$\frac{d}{2}$$​=$$\frac{21 {\text{cm}}} { 2 }$$=  10.5 cm

$$\text {Surface area} = 4πr² = 4 \times \frac{22}{7} \times (10.5)^2 = 4 \times \frac{22}{7} \times 110.25 = \frac{88}{7} \times 110.25 = 1386\ \text{cm}^2$$​​