9. A farmer connects a pipe of internal diameter 20 cm from a canal into a cylindrical tank in her field, which is 10 m in diameter and 2 m deep. If water flows through the pipe at the rate of 3 km/h, in how much time will the tank be filled?
Area of the cross-section of pipe is
Speed of water is given to be = 3 km/hr
Thus, the volume of water flowing through a pipe in 1 min. is
Now let us assume that tank will be completely filled after t minutes.
Then we write :
Hence time required for filling of the tank completely is 100 minutes.