Question

The area of a circle is 1381 m². Find its circumference.

Answer 1

Let the radius of the circle be r m.
Then, area = ${\mathrm{\pi r}}^2$ m²
∴ ${\mathrm{\pi r}}^2$ = 1386
⇒ $\left(\frac{22}{7}\times r\times r\right)$ = 1386
⇒ r² = $\left(\frac{1386\times 7}{22}\right)$ = 441
⇒ r = $\sqrt{441}$ = 21
⇒ Circumference of the circle = $\left(2\mathrm{\pi r}\right)$ m
= $\left(2\times \frac{22}{7}\times 21\right)$ m = 132 m