Question
A drain pipe can drain a tank in 12 hours, and a fill pipe can fill the same tank in 6 hours. A total of n pipes – which include a few fill pipes and the remaining drain pipes – can fill the entire tank in 2 hours. How many of the following values could ‘n’ take
CAT 2021
Solution
Correct option is
(A)
Explanatory Answer
The two drain pipes can drain the same volume that one fill pipe fills , which mens that a D-D-F combination has to have a net volume effect of 0
hence only the fills pipes can manage to fill the tank . as we want all the net zero effect pipes , we want three more fill pipes to fill the tank in 2 hours
so , we can have as many D-D-Fs as we want , but we need one F-F-F at the end to ensure tank to fill in 2 hrs
then the no. of pipes will be (D- D-F).....(D- D-F) + (F- F-F)
hence we can say that no. of pipes should be multiple of 3.
so , A option is correct.
