Question

Water in a canal, 5.4 m wide and 1.8 m deep, is flowing with a speed of 25 km/hour. How much area can it irrigate in 40 minutes, if 10 cm of standing water is required for irrigation?

Answer 1

Width of the canal = 5.4 m

Depth of the canal = 1.8 m

Height of the standing water needed for irrigation = 10 cm = 0.1 m

Speed of the flowing water = 25 km/h = `25000/60=1250/3` m/min

Volume of water flowing out of the canal in 1 min

= Area of opening of canal  x `1250/3`

`= 5.4 xx 1.8 xx 1250/3`

=4050 m³

∴ Volume of water flowing out of the canal in 40 min = 40 × 4050 m³ = 162000 m³

Now,

Area of irrigation = `"Volume of water flowing out from canal in 40 min"/"Height of the standing water needed for irrigation"`

`= 162000/0.1`

`= 1620000 m^2`

= 162 hectare   (∵ 1 hectare = 10000 m²)

Thus, the area irrigated in 40 minutes is 162 hectare.