Question

A road 3.5m wide surround a circular plot whose circumference is 44m. Find the cost of paving the road $20 per m square.(Take pie as 22/7)

Answer 1

$circumference \: of \: plot \: = 44m \\ 2\pi \: r = 44 \\ r = \frac{44 \times 7}{22 \times 2} \\ r = 7 \\ area = \pi \: {r}^{2} \\ road \: radius = 7 + 3.5 \\ = 10.5 \\ area \: of \: road = \frac{22}{7} \times 10.5 \times 10.5 \\ = 346.5 \\road = 345.5 - 154 \\ = 192.5 \\ cost = 192.5 \times 20 \\ = 3850$