Question

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

Answer 1

Given:

• The width of the canal = 300m = 3m
• Depth of the canal = 120cm = 1.2m
• Speed of the canal's water = 20km/h

20 km/h = 20 × 1000 m/h = 20000 m/h

So,

$\boxed{1m = 100cm}\ or\ i.e.\ \boxed{ 1cm = \frac{1}{100}m}$

$\boxed{1km = 1000m}$

Now,

The Volume of water that flows in the canal in one hour

= Width of the canal × Depth of the canal × Speed of the water in the canal.

$= \bf 3 \times 1.2 \times 20000$

$= \bf 72000m^3$

Now,

In 20 minutes, the volume of the water that flows in the canal will be

$= 72000 \times \frac{2\not0}{6\not0}$

$= \boxed{24000m^3}$

Now,

The area irrigated in 20 minutes if 8 cm or 0.08m standing water is needed -

$= \bf \frac{24000}{0.08} = 300000m^{2}$

$= \bf 30\ hec$

∵ [As 1 hec = 10000m²]