Question

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 the half of the tabk if it is 3m in diameter

Answer 1

Diameter= 3m
Radius= 3÷2= 1.5m
Vol.= 2/3 πr cube
Let it take x sec to empty the whole tank

Vol. Emptied in x seconds = Vol. Of tank

Also vol of tank = 25/7 litre × x seconds

25/7 litres = 25000/7 cm cube

Therefore 25000/7 × x= vol of tank
25000/7 × x= 2/3 π × 1.5
Therefore by solving the above equation we get
X = 1980 seconds
ie: time for emptying whole tank = 1980 seconds
Time for emptying half the tank = 1980÷ 2= 990seconds

Answer 2

Answer:

989 seconds

Step-by-step explanation:

Radius =1.5m

Volume of the tank = (2/3)πr³

=(2/3)(3.14)(1.5)³

=7.065m³

=7065 L

Time taken to half the tank at the rate of 25/7 L/s

=(1/2)(7065)(25/7)

=989 seconds