Question

The cost of fencing a circular field at the rate of Rs. $24$ per metre is Rs. $5280$. The field is to be ploughed at rate of Rs. $2$ per $m^2$. Find the cost of ploughing the field.

Answer 1

Let the radius of circular field $=r$

$\therefore$ total circumference $=2\pi r$

$\therefore 2\pi r\times 24=Rs.5280$

$\therefore \pi r=\frac{5280}{2\times 24}$

$\therefore r=\frac{5280}{\left(48\right)\pi }$

$\therefore r=\frac{5280\times 7}{\left(48\right)\times 22}$

$\therefore$ radius $=35m$

$\therefore$ now total area $=\pi r^2$

$\therefore$ area $=\frac{22}{7}\times 35\times 35$

$\therefore$ area $=110\times 35$

$\therefore$ area $=3850m^2$

$\therefore$ total cost $=2\times 3850$

$\therefore$ total cost $=7700Rs.$