Question

Water in a canal, 30 dm wide and 12 dm deep is flowing with velocity of 10 km/hr. How much area will it irrigate in 30 minutes, if 8 cm of standing water is required for irrigation?

Answer 1

Width of the canal = 30 dm = 300 cm = 3 m

Depth of the canal 12 cm = 120 cm = 1.2 m

It is given that the water is flowing with velocity 10 km/hr

Therefore Length of the water column formed is 1/2 hour = 5 km = 5000 m

Therefore volume of the water flowing in 1 hour

= Volume of the cuboid of length 5000 m, width 3 m and depth 1.2 m

=> Volume of the water in half hour = (5000*3*1.2) m^3 = 18000 m^3

Suppose x m^2 area is irrigated in 1/2 hour

x*8/100 = 18000

x = 1800000/8

x = 225000

Hence the canal irrigated 225000 m^2 area in 1/2 hours