A hemispherical tank , full of water , is emptied by a pipe at the rate of 25/7 litres per second. How much time will it take to empty half the tank if the diameter of the base of the tank is 3 m ?
volume of hemisphere=2/3 πr³
=2/3 * 22/7 * (3/2)³ =99/14 m³
vol. of water that would be emptied=1/2 of vol.of hemispherical tank
=1/2 *99/14 =99/28 m³
vol.=99/28 m³ *1000 litres
in 1 second as 25/7 litres of water would be emptied
so,99000/28 litres of water would be emptied in =99000/28 *7/25
Diameter of Hemispherical Tank=3m
So, Radius of Hemispherical Tank=3/2m
Volume of Hemispherical Tank=2/3πr3
On solving, We get Volume of Hemispherical Tank= 99/14m3
Half the volume of Tank= 99/28m3
Now, 1m3=1000 Liters
This Implies, if 25/7 litres of water is emptied in 1sec,
So, 1 Litres of water will be emptied in 7/25 sec (Unitary Method of solving)
So, 1/2 the volume of Hemispherical Tank i.e.99000/28 Litres will be emptied in:
Which is equal to=990 seconds or 16 Minutes 30 seconds.........
Hope, My answer is correct and You will understand it Easily!!