Question

Find the circumferences of the circles from their radii given below.

(1) 56 cm
(2) 7.7 cm
(3) 2.8 cm

Answer 1

(1) Radius of the circle is 56 cm.
Circumference of a circle = 2πr
Circumference = 2 × π × 56 cm
= $\frac{22}{7}$ × 2 ×56 $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
= 352 cm
∴ Circumference of the circle is 352 cm.

(2) Radius of the circle is 7.7 cm.
Circumference of a circle = 2πr
Circumference = 2 × π × 7.7 cm
= $\frac{22}{7}$ × 15.4 $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
= 48.4 cm
∴ Circumference of the circle is 48.4 cm.

(3) Radius of the circle is 2.8 m.
Circumference of a circle = 2πr
Circumference = 2 × π × 2.8 m
= $\frac{22}{7}$ × 5.6 $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
= 17.6 m
∴ Circumference of the circle is 17.6 m.