Circular Field Fencing and Area - Part (b)

$\text{Perimeter of the field} = \frac{\text{Total cost of fencing}}{\text{Rate per metre}} = \frac{6000}{30} = 200\text{ m}$

Perimeter = $2\pi r = 200\text{ m}$. $2 \times \frac{22}{7} \times r = 200 \implies r = \frac{350}{11} \approx 31.82\text{ m}$

Area of the field = $\frac{35000}{11}\text{ m}^2$. $\text{Cost of ploughing} = \text{Area} \times \text{Rate} = \frac{35000}{11} \times 0.50 = \frac{17500}{11} \approx \text{₹ } 1590.91$