Water is flowing at the rate of 7 m/s.
o length of pipe in which the water has traveled,
h = 7(1800) = 12600m
Radius of the pipe(r)= 1cm
Radius of the cylinder(R)= 40 cm

let the height of the water in the tank H
Volume of water coming from the pipe = Volume of water in the cylindrical tank.

πr^2h = πR^2h
H = {(0.01)^2 X 12600}/(0.4)^2 = 7.875m (ans)

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Here to find the height You should put the formula V. of cylindrical tank = Area of cross section x Speed of flowing water x time

rate of flow =7m s- for pipe:
radius = 1cm or 0.01m for tank :
 radius = 40cm or 0.4m time = 1/2hr = 30min =1800sec according to formula area of cross section = area of pipe *speed * time
pi r2h = pi R2 * 7*4800
h = 0.01*0.01*7*1800/0.4*0.4
h= 7.875
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