Question

Water in a canal, 6 m wide and 1.5 m deep, is flowing with a speed of 10 km/hour. How much area will it irrigate in 30 mins; if 8 cm standing water is needed?

Answer 1

Depth of the canal = 1.5 m
Length of the water column formed in `1/2` hr
= % km or 5000 m

∴ The volume of water flowing in `1/2` hr

= Volume of a cuboid of length 5000 m, width 6 m, and depth 1.5 m.
= 5000 x 6 x 1.5 = 45000 m³ 

On comparing the volumes, 

The volume of water in the field = Volume of water coming out from canal in 30 minutes.

Irrigated area x standing water = `45000/(8/100)`  [∵ 1m = 100 cm]

`(4500xx100)/8 = 5,62,500"m"^3`