Question

A circular grass plot of land $42m$ is diameter has a path $3.5m$ wide running round its outside. Find the cost of gravelling the path at $Rs.4$ per square metre.

Answer 1

Area of inner circle$=\pi r^2=\frac{22}{7}\times 21\times 21=22\times 3\times 21=1386$sq.m

Area of outer circle$=\pi r^2=\frac{22}{7}\times 24.5\times 24.5=22\times 24.5\times 2.5=1886$sq.m

Area of path$=1886-1386=500.5$sq.m

Cost of gravelling $=500.5\times 4=$Rs.$2002$