A cylindrical tank full of water is emptied by a pipe at the rate of 225 liters per minute. How much time will it take to empty half the tank, if the diameter of its base is 3 m and its height is 3.5 m? 
Diameter of the cylindrical base =3 m
∴ Radius of cylindrical tank 
m
= 1.5 m
Height of the tank =3.5 m
Volume of the tank 
= 24.75 m3
Now, 1 m3 = 1000 liters
24.75 m3 =1000 × 24.75 liters
= 24750 liters
Full quantity of the water when it is full = 24750 m3
Quantity of water when it is half filled
liters
= 12375 liters
Time taken by it to empty 225 liters 0f water = 1 minute
∴ Time taken by it empty 12375 litersof water = 
minutes
= 55 minutes
50