A circular grass plot of land 42 m is diameter has a path 3.5 m wide running round its outside. Find the cost of gravelling the path at Rs.4 per square metre.
Area of inner circle=πr2=227×21×21=22×3×21=1386sq.m
Area of outer circle=πr2=227×24.5×24.5=22×24.5×2.5=1886sq.m
Area of path=1886−1386=500.5sq.m
Cost of gravelling =500.5×4=Rs.2002