Solution: Water in the canal form a cuboid of breadth = 12 dm = 12/10 m = 1.2 m ,
height =30 dm = 30/10 m = 3 m
and , Length = Distance covered by water in 30 minutes
= Velocity of water time
Volume of water flown in 30 min
Suppose area irrigated be Then ,
Volume flown in 30 minutes.
Hence , area irrigated = 400000