Q14 of 24 Page 236

Water in a canal 30dm wide and 12dm deep is flowing with a velocity of 20km/h. How much area will it irrigate in 30 minutes if 9 cm of standing water is desired?

Given,


Depth(d) = 12dm = 1.2m


Width(w) = 30dm = 3m


Velocity of water (v) = 20km/h = 20,000 m/h


time (t) = 30minute = 0.5 hour


⇒ The volume of water = w × d × length


Here length becomes speed × time = v × t


Volume of water = w × d × v × t


= 1.2 × 3 × 20000 × 0.5


= 36000 m3


Now,


Let the area irrigated be x


And Desired standing water = 9cm = 0.09m


Since volume of water will be same


⇒ 36000 = x × 0.09


⇒ x = 400000


So, area irrigated by the canal is 400000 m2


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