this is the correct answer

Given, internal diameter of cylindrical pipe = 2 cm

So, radius of cylindrical pipe (r) = 2/ 2 = 1 cm

Area of cross section of pipe= r^{2}= (1)^{2}= cm^{2}

Speed of water= 0.4 m/s =0.4 x 100 cm/s = 40 cm/s

Thus,

Volume of water flown out in half an hour = x 40 x 30 x 60 = 72000 cm^{2}

And,

Radius of cylindrical tank (R) = 40 cm

Let level of water rise to the height of h cm.

Thus,

Volume of cylindrical tank = R^{2}h = (40)2h = 1600h cm^{2}.

Now,

Volume of cylindrical tank = Volume of water flown out in half an hour

1600h = 7200

h = 45cm

Hence, level of water rise to the height of 45 cm.

Hope it helps

Thankyou

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