Question

Find the surface area of a sphere of radius
(i) $10.5$cm (ii) $5.6$cm (iii) $14$cm

Answer 1

(i) $r=10.5$cm
SA$=4\pi r^2=4\times \frac{22}{7}\times \frac{10.5}{10}\times \frac{10.5}{10}$
$=\frac{88\times 15\times 105}{100}$

$=1386$ cm${}^2$

(ii) $r=5.6$cm
SA$=4\pi r^2$
$=[4\times \frac{22}{7}\times {\left(5.6\right)}^2]$cm${}^2$
$=[\frac{88}{7}\times \frac{5.6}{10}\times \frac{5.6}{10}]$cm${}^2$

$=394.24$ cm${}^2$

(iii) $r=14$cm,
SA$=4\pi r^2$
$=4\times \frac{22}{7}\times 14\times 14$

$=2464$ cm${}^2$