Question

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

Answer 1

to find the height of pipe,

3km -----> 1 hr

3000m ------> 60 mins

=> 1 min ----> 3000 / 60

1 min ----->  50m

radius of pipe = 0.1 m

volume of pipe = π r² h

= π * (0.1) * (0.1) * 50

height of cistern = 2m

radius = 5m

volume of cistern = π r² h

= π * 5 * 5 * 2

let time taken be "t"

t = volume of cistern / volume of pipe

t =      π * 5 * 5 * 2  /  π * (0.1) * (0.1) * 50

t  = 100 mins

100 mins = 1 hr 40 mins