The cost of fencing a square field with the rate of Rs  20 per metre is Rs  10080. How much will it cost to lay a three-metre-wide pavement along the fencing inside the field at a rate of Rs 50 per sq metre?

Given:

Total cost of fencing = Rs. 10080

Cost of fencing per metre = Rs. 20

Concept used:

Perimeter = Total cost / Cost per metre

Area of the pavement = area of outer square - area of inner square.

Calculation:

According to the question,

Total cost of fencing = 10080

Perimeter of square = 10080/20 = 504 m

⇒ Side of square = 504/4 = 126 m

According to the diagram,

Breadth of the pavement = 2 × 3m = 6m

Side of inner square = 126 - 6 = 120m

Area of pavement = (126 × 126) - (120 × 120)

⇒ Area of pavement = 1476

Cost of pavement = 1476 × 50 = Rs. 73800.

∴ The cost of pavement is Rs. 73800.