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

Width of the canal = 6 m

Depth of the canal = 1.5 m

Length of water column per hour = 10 km

Length of water column in 30 minutes or $$\frac{1}{2}$$ hour $$= \ \frac{1}{2} \ × \ 10 \ = \ 5000$$ m

Volume of water flown in 30 minutes $$= \ 1.5 \ × \ 6 \ × \ 5000 \ = \ 45000$$ m3

$$\because$$ $$8$$ cm $$= \ \frac{8}{100}$$ m

i.e., 0.08 m standing water is desired

$$\therefore$$ Area irrigated in 30 minutes

$$= \ \frac{Volume}{Height} \ = \ \frac{45000}{0.08} \ = \ 562500$$ m2 or $$56.25$$ hectares