Question

If the area of a circle is $38.5m^2$, then its circumference will be

• A. $22$
• B. $2.2$
• C. $38.5$
• D. $3.85$

Answer 1

Answer: (A)

$22$

Area of a circle $=\pi r^2$
$\therefore 38.5=\pi r^2$
$\therefore \frac{22}{7}\times r^2=38.5$
$\Rightarrow r^2=38.5\times \frac{7}{22}$
$\Rightarrow r^2=12.25\Rightarrow r=\sqrt{12.25}$
$\therefore$ $r=3.5$
Now, Circumference of circle $=2\pi r$
$\therefore$ Circumference of circle $=2\times \frac{22}{7}\times \frac{35}{10}$
$\therefore$ Circumference of circle $=22m$