Question

Find the area of a circle whose diameter is

(i) 28 cm.
(ii) 1.4 m.

Answer 1

(i) Given:
d = 28 cm ⇒ r = $\left(\frac{d}{2}\right)$ = $\left(\frac{28}{2}\right)$ cm = 14 cm
Area of the circle = $\left({\mathrm{\pi r}}^2\right)$ sq. units
= $\left(\frac{22}{7}\times 14\times 14\right)$ cm² = $\left(22\times 2\times 14\right)$ cm² = 616 cm²

(ii) Given:
r = 1.4 m ⇒ r = $\left(\frac{d}{2}\right)$ = $\left(\frac{1.4}{2}\right)$m = 0.7 m
Area of the circle = $\left({\mathrm{\pi r}}^2\right)$ sq. units
= $\left(\frac{22}{7}\times 0.7\times 0.7\right)$ m² = $\left(22\times 0.1\times 0.7\right)$ m² = 1.54 m²