Let R cm be the radius and H cm be the height of a circular pipe, then
H (depth) = 3 km = 3000 m.Now, Volume of water that flows out of the circular pipe in 1 hour = πR2HLet r m be the radius and h m be the depth (height) of a circular cistern, then
Now, Volume of water that flows in the circular cistern= π r2h= π x 5 x 5 x 2 = 50 π m3.Hence,Time taken to fill up the cistern