Question

Find the surface area of a sphere of diameter:
(i) $14$ cm (ii) $21$ cm (iii) $3.5$ m.

Answer 1

$\left(i\right)$ $r=\frac{d}{2}=\frac{14}{2}=7$cm,

$\Rightarrow$Surface Area$=4\pi r^2$

$=4\times \frac{22}{7}\times 7\times 7$

$=616$cm${}^2$

$\left(ii\right)$ $r=\frac{21}{2}=10.5cm$,

$\Rightarrow$Surface Area$=4\times \frac{22}{7}\times 10.5\times 10.5$

$=1386$cm${}^2$

$\left(iii\right)$ $r=\frac{3.5}{2}=1.75m$

$\Rightarrow$Surface Area$=4\pi r^2$

$=4\times \frac{22}{7}\times \frac{1.75}{100}\times \frac{1.75}{100}$

$=38.5$m${}^2$