A square field has an area of 1.44 hectares. Find the cost of fencing it right round at ₹25 per metre. Take 1 hectare = $10000{\text{m}}^2$.

1.44 hectares = $14400{\text{m}}^2$, so the side = √14400 = 120 m and the perimeter = $4\times 120=480$ m. Cost = $480\times 25$ = ₹12000. (Using $2\times 120=240$ m, half the way round, gives ₹6000; fencing one side only gives ₹3000; charging the $14400{\text{m}}^2$ of ground at the per-metre rate gives ₹360000.)