A cistern can be filled by pipe P in 3 hours and pipe Q in 5 hours and empty by pipe R in 2 hours. If all these pipes are open, then in how many hours the cistern will be full?
A cistern can be filled by pipe P in 3 hours and pipe Q in 5 hours and empty by pipe R in 2 hours. If all these pipes are open, then in how many hours the cistern will be full?
[A]10 hours
[B]15 hours
[C]30 hours
[D]Cannot be filled
30 hours
Because as per the question part of the cistern filled by all pipes in an hour $latex = \frac{1}{3}+\frac{1}{5}-\frac{1}{2}=\frac{10+6-15}{30}=\frac{1}{30}&s=1$
So, the cistern will be filled in 30 hours if all pipes are open.
Hence option [C] is correct answer.