A circular pond of diameter 40 meters is surrounded by a grass path 5 meters wide. Find the area of this path.
Solution: The radius of the inner circle, which is a pond, is 20 m and the radius of the outer circle is 20 + 5, i.e., 25 m, as it includes the path. We have to find the area of the path, i.e. of the annulus thus made.
Therefore, the area of the path = Π R2 - Π r2 = Π (R + r)(R - r)
= 22 / 7 x (25 + 20)(25 - 20) m = 22 / 7 x 45 x 5 = 4950 / 7 = 707.14 m2