The cost of cultivating a square field at the rate of Rs. 685 per hector is Rs. 6165. The cost of putting a fence around it at the rate of Rs. 48.75 per metre would be :

$$\eqalign{ & {\text{Area}} = \frac{{{\text{Total cost}}}}{{{\text{Rate}}}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\, = \left( {\frac{{6165}}{{685}}} \right){\text{hectares}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\, = \left( {9 \times 10000} \right){m^2} \cr} $$
∴ Side of the square :
$$\eqalign{ & = \sqrt {90000} \,m \cr & = 300\,m \cr} $$
Perimeter of the field = (300 × 4) m = 1200 m
Cost of fencing = Rs. (1200 × 48.75) = Rs. 58500