There are 8 filling pipes each capable of filling a cisterns alone in 5 minute and 6 empting pipes each capable of empting a cistern in 6 minutes.

There are 8 filling pipes each capable of filling a cistern alone in 26 minutes and 6 emptying pipes each capable of emptying a cistern alone in 24 minutes. All pipes are opened together and as a result, tank fills 27 litres of water per minute. Find the capacity of the tank.

a)445 L
b)458 L
c)460 L
d)468 L
e)None of these

ANSWER:    468 L

Firstly we have to calculate one minute work for all pipes together. The equation is :

8/26  –  6 / 24  =  3/52   for a minute  all pipes together.  Then calculate tank capacity.

if  3/52   =   27 litres   then 52/52 =   27 / (3/52) =  468 L