Question

From the given circumferences, find the radii and the diameters of the circles.

(1) 198 cm
(2) 616 cm
(3) 72.6 m

Answer 1

(1) Circumference of the circle is 198 cm.
Circumference of a circle = 2πr
Circumference = 2 × π × r
198 = $\frac{22}{7}$ × 2 × r $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
r = 31.5 cm
d = 2 × r
= 63 cm
∴ Radius of the circle is 31.5 cm.
Diameter of the circle is 63 cm.

(2) Circumference of the circle is 616 cm.
Circumference of a circle = 2πr
Circumference = 2 × π × r
616 = $\frac{22}{7}$ × 2 × r $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
r = 98 cm
d = 2 × r
= 196 cm
∴ Radius of the circle is 98 cm.
Diameter of the circle is 196 cm.

(3) Circumference of the circle is 72.6 m.
Circumference of a circle = 2πr
Circumference = 2 × π × r
72.6 = $\frac{22}{7}$ × 2 × r $\left(\mathrm{Taking}\mathrm{\pi }=\frac{22}{7}\right)$
r = 11.55 m
d = 2 × r
= 23.1 m
∴ Radius of the circle is 11.55 m.
Diameter of the circle is 23.1 m.