Question

Find area of circle whose diameter is 21 cm

Answer 1

radius= 10.5 cm since diameter = 21 cm.
$area \:of \: a \: circle \: = \pi {r}^{2}$
so,
Area = 22/7 * 10.5 * 10.5
= 346.5 cm^2 .
hope this helps...

Answer 2

radius = d / 2=21 /2
area = pi r "2
= 22/7 × 21/2 ×21/2