Question

2. Find the radius and circumference of a circle, whose area is :

(i) 154 $c{m}^2$ (ii) 6.16 $m^2$

Answer 1

Area of circle $=154c{m}^2$

$\pi r^2=154$

$r^2=\frac{154}{\pi }$

$r^2=\frac{154}{22}\times 7$

$r^2=7\times 7$

r =7 cm

$\therefore$ circumference $=2\pi r$

$=2\times \frac{22}{7}\times 7$

=44 cm

Hence 7 cm; 44 cm

(ii)Area of circle $=6.16m^2$

$\pi r^2=6.16$

$\frac{22}{7}{r}^2=\frac{616}{100}$

$r^2=\frac{616}{100}\times \frac{7}{22}$

$r^2=\frac{196}{100}$

$r^2=1.96$

$r=\sqrt{1.96}$

r=1.4 m

Circumference $=2\pi r$

$=2\times \frac{22}{7}\times 1.4$

=8.8 m

$\therefore 1.4m$; 8.8 m