Question

The flow of water in a canal of breadth 30 m and depth 12 dm is 20 km/h. If 9 cm height of water is needed in fields, then how much area of a field will be watered with in 30 minutes.

Answer 1

Given,

Breadth of canal = 30 dm = 3 m

Depth of the canal = 12 dm = 1.2 m

The length water flowing in one hour 

= 20 km = 20,000 m

The length of water flowing in 30 minutes 

= \(\frac { 20000 }{ 2 }\) = 10000 m.

The volume of the water flow in 30 minutes 

= 10000 × 3 × 1.2

Let the area of water be A.

And the height of the water in the filed = 9 cm 

= \(\frac { 9 }{ 100 }\) m

Volume of water required = A × \(\frac { 9 }{ 100 }\)

Hence, the area of watered = 4,00,000 m²