Question

If the area of a circle is 78.5 ${cm}^2$, Finds its circumference . $(Take\pi =3.14)$

Answer 1

$A=\pi r^2$

$\Rightarrow 78.5=3.14r^2$

$\Rightarrow 25=r^2$

So $r=5$

$c=2\pi r$

$=2\times 3.14\times 5$

$=31.4$cm.