Question

A square tank of capacity 250m^3 has to be dug out . the cost of the land is rs 50/m^2

Answer 1

As the question says that the tank is square in shape so it must be a cubical tank of edge a
thus volume of tank = capacity
  
a^3 = 250 m^3
   a = 15.81 m
we can calculate the area taken by the tank on land

Area = a^2
         = 15.81^2
        =  249.95 m Sq

According to question

Cost of 1 m^2 of land  = Rs 50
So cost of 249.95 m sq of land = 50*249.95
                                                  = 12497.805 Rs
Thus cost of land for the tank = 12497.805 Rs

Answer 2

Solution :-

Capacity of the square tank = 250 m³

Square tank is in the shape of cube.

So, 

Volume of the Cube = a³

250 = a³

a = ∛250

a = 6.299 m

Now, for computing the cost of digging the land, we have to calculate the lateral surface area.

Lateral Surface Area of Cube = 4a²

⇒ 4*(6.299)²

⇒ 4*39.677

= 158.708 m²

Lateral surface area of cube is 158.708 m²

Cost of digging = Rs. 50 per sq m

Total cost = 50*158.708

= Rs. 7935.4

Answer.