Explain how tosolve questions like : -Water is flowing at the rate of 3 km/h through a circular pipe of 20 cm internal diameter into a circular cistern if diameter 10m and depth 2m . In how much time will the cistern be filled ?

internal radius of the pipe = 10cm = 1/10 m
Since, water is flowing at the rate of 3 km/h.
In one minute it covers distance = 3 km = 3000m
Volume of water flowing in one minute = (pi) r²h
= (pi) x 1/10 x 1/10 x 3000
= 30 (pi)

Radius of circular cistern = 5 m
Depth of the circular cistern = 2 m
Volume of water can be stored in it = (pi) r²h
= (pi) x 5 x 5 x 2
= 50 (pi)

Time taken to fill the cistern = Volume of cistern / Volume of the pipe
= 50 (pi) / 30 (pi) 
= 5/3 hours 
= 100 minutes


HOPE IT HELPS..