#### Question Water in a canal, 5.4 m wide and 1.8 m deep, is flowing with a speed of 25km/hour. How much area can it irrigate in 40 minutes, if 10 cm of standing water is required for irrigation?

#### Video Explanation

#### Explanatory Answer

Volume of water flowing in the canal in 40 minutes = volume of water used for irrigation.

Length of water column formed in 40 minutes = 25 × 1000 × \\frac{40}{60}) = \\frac{50,000}{3}) m

##### How did we get the last step?

Water flows at the rate of 25 km/hr. We have convered 25 km to (25 × 1000) m.

We divided the above answer by 60 to find the length of water column formed every minute.

Finally multiplied it by 40 to find the length of water column formed in 40 minutes.

Volume of water flowing in 40 minutes = cross section area of pipe × length of water column

= 5.4 × 1.8 × \\frac{50,000}{3}) m^{3} ......... (1)

Volume of water used for irrigation = area of field × height of water required for irrigation

= area of field × \\frac{1}{10}) m^{3} ......... (2)

Equate volume of water in equations (1) and (2).

5.4 × 1.8 × \\frac{50,000}{3}) = area of field × \\frac{1}{10})

Area of field = 54 × 18 × \\frac{5,000}{3})

Area of field = 324 × 5000

Area of field irrigated = 1,62,000 m^{2}