The cost of fencing a square field at 60 paise per metre is Rs 1200.
Question:

The cost of fencing a square field at 60 paise per metre is Rs 1200. Find the cost of reaping the field at the rate of 50 paise per 100 sq. metres.

Solution:

Given:

Cost of fencing 1 metre of a square field $=60$ paise

And, the total cost of fencing the entire field $=$ Rs $1200=1,20,000$ paise

$\therefore$ Perimeter of the square field $=\frac{120000}{60}=2000$ metres

Now, perimeter of a square $=4 \times$ side

For the given square field :

$4 \times$ Side $=2000 \mathrm{~m}$

Side $=\frac{2000}{4}=500$ metres

$\therefore$ Area of the square field $=500 \times 500=250000 \mathrm{~m}^{2}$

Again, given: Cost of reaping per $100 \mathrm{~m}^{2}=50$ paise

$\therefore$ Cost of reaping per $1 \mathrm{~m}^{2}=\frac{50}{100}$ paise

$\therefore$ Cost of reaping $250000 \mathrm{~m}^{2}=\frac{50}{100} \times 250000=125000$ paise

Thus, the total cost of reaping the complete square field is 125000 paise, i.e. Rs 1250 .