Question

Water in a canal, 6 m wide and 1.5 m deep, is flowing with a speed of 10

km/h. How much area , in hectare, will it irrigate in 30 minutes, if 9 cm of

standing water is needed?​

Answer 1

★ Speed of flowing of water from canal = $\bf{10 km/h}$

★ Length of water flowing in 1 hour = $\bf{5 km}$

★ Length of flowing water in 30 minutes = $\bf{5 km}$

Now,

✔ Volume of water flowing from canal = Length of water flowing in 30 minutes × Breadth of canal × Deep of canal

$\\ :\implies{\sf{5000m \times 6m \times 1.5m}} \\ \\ :\implies{\sf{45000 {m}^{3} }}$

Let us assume area of field be x m²

✔ Volume of water irrigates into field = Area of field × height of water during irrigation

$\\ :\implies{\sf{x {m}^{2} \times 8 \times {10}^{ - 2} m}} \\ \\ :\implies{\sf{0.08x {m}^{3} }}$

Thus,

✔ Volume of water flowing from canal = volume of water in field

$\\ :\implies{\sf{45000 {m}^{3} = 0.08x {m}^{3}}} \\ \\ :\implies{\sf{562500 {m}^{2} }}$

We know that,

✔ 1 Hectare = 10000 m²

$\\ :\implies{\sf{\dfrac{\cancel{562500}}{\cancel{10000}}}} \\ \\ :\implies{\sf{56.25}}$

Hence,

• In 56.25 Hectares it will irrigate in 30 minutes if 9cm of standing water is needed.