Water in a canal 30 dm wide and 12 dm deep, is flowing with a velocity of 100 km per hour. How much area will it irrigate in 30 minutes if 8 cm of standing water is desired?
Given,
Width of canal = 30 dm = 3m
Depth of canal = 12 dm = 1.2 m
Velocity of flow = 100 km/h
Length of cuboid thus formed = distance travelled by water in 30 minute at speed 100km/h
=
Volume of water = 50000×3×1.2 m3
Water accumulated in field forms a cuboid of base area equals to area of field and height = 
= hence , area of field = 
9