Question

Because of the water resources away from the village, the vilagers built an underground water canal to fill the well in which water flows with 2m/s and its width is 30cm and length 80 cm. How much time will it take to fill one well of radius 3m and 21 m deep?

Answer 1

Solution:-

Width of the canal = 30 cm = 0.3 m
Length of the canal = 80 cm = 0.8 m
Area of the canal = 0.3*0.8
= 0.24 m²
Volume of the well = πr²h
= 22/7*3*3*21
= 594 m³

Let the time taken to fill the well of radius of 3 m and depth of 21 m be 'x'
Rate of water flow = 2 m/s 
Area of canal*Water flow*x = 594
⇒ 0.24*2*x = 594
⇒ 0.48x = 594
⇒ x = 594/0.48
⇒ x = 1237.5 
1237.5/60 = 20.625 minutes
So, the time taken is 1237.5 seconds or 20.625 minutes.
Answer.