Water in a canal, `30\ d m\ w i d e\ a n d\ 12 d m\ d e e p ,\ ` is flowing with a velocity of `20 k m\ p e r\ hou rdot` How many area will it irrigate in `30\ m in ,\ ` if `9\ c m` of standing water is desired?

Answer

`400000 m^(2)`

Explanation

Distance covered by water in 30 minutes
= velocity of water in m/hr `xx` time in hours
`= (20000 xx (30)/(60)) m = 10000m`
Volume of water flown in 30 min `= (10000 xx (30)/(10) xx (12)/(10)) m^(3) = 36000 m^(3)`
Let the area irrigated be x `m^(2)`
Then, `x xx (9)/(100) = 36000 rArr x = (36000 xx (100)/(9)) m^(2) = 400000 m^(2)`