Question

A canal is 300 cm wide and 120 cm deep. The water in the canal is flowing with a speed of 20 km/hr. How much area will it irrigate in 20 minutes if 8 cm of standing water is desired ?

Answer 1

Width of the canal = 300 cm = 3 m
Depth of the canal = 120 cm = 1.2 m
Speed of water flow = 20 km/h = 20000 m/h
Distance covered by water in 1 hour or 60 min = 20000 m
So, distance covered by the water in 20 min =  \[\frac{20}{60} \times 20000 = \frac{20000}{3}m\]

Amount of water irrigated in 20 mintues \[= 3 \times 1 . 2 \times \frac{20000}{3} = 24000\]m³

Area irrigated by this water if 8 cm of standing water is desired will be \[\frac{24000}{\frac{8}{100}} = 300000 m^2\]

So, area irrigated will be 300000 m² or 30 hectors.