Question

Water is flowing at the rate of 3 km/hr through a circular pipe of 20 cm internal diameter into a circular cistern of diameter 10m and depth 2m. In how much time will the cistern be filled?

Answer 1

Rate of flow of water = 3 km/hr = 50 m/min

Let the time taken by the pipe to fill the cistern be x min.

Diameter of pipe,d=20cm =0.2m

Radius of the pipe, r =0.1m

The radius of cistern,R= 5m

Height of cistern,h = 2m

Let the height of pipe be 50x m

Volume of pipe = Volume of cistern

2pie rH = 2pieRh

50x × 0.1= 2 × 5

5x=10

x= 2 minutes