Find the area of a flat circular ring formed by two concentric circles (circles with same centre) whose radii are 9 cm and 5 cm.

Given:

Radius of outer circle = 9 cm

Radius of inner circle = 5 cm

Area of circular ring = Area of outer circle - Area of inner circle

As we know, the area of the circle = πr²

Area of circular ring =

$\dfrac{22}{7} \times 9^2 - \dfrac{22}{7} \times 5^2\\[1em] = \dfrac{22}{7} \times 81 - \dfrac{22}{7} \times 25\\[1em] = \dfrac{1,782}{7} - \dfrac{550}{7}\\[1em] = \dfrac{1,782 - 550}{7}\\[1em] = \dfrac{1,232}{7}\\[1em] = 176 \text{ cm}^2$

Hence, the area of the circular ring is 176 cm².