A rectangular field is 150 m long. The cost of fencing it at the rate of rupees 60 per meter is rupees 120,600, find the area in square metre.

Given: 

A rectangular field is 150 m long. The cost of fencing it at the rate of rupees 60 per meter is rupees 120,600

To do: 

We have to find the area of the field.

Solution:

 Let the breadth of the rectangular field be $b$.

Total cost of fencing $=Rs.\ 120600$

Cost of fencing $1\ m^2=Rs.\ 60$

Perimeter of the field $=2(150+b)$

$300+2b=\frac{120600}{60}$

$300+2b=2010$

$2b=2010-300$

$2b=1710$

$b=\frac{1710}{2}$

$b=855\ m$

Therefore,

Area of the rectangular field $=150\times855\ m^2$

$=128250\ m^2$

The area of the field is $128250\ m^2$.