RRB Paramedical Staff Nurse Model Paper 4

Question : 43 of 100

Marks: +1, -0

Two pipes A and B can separately fill a cistern in 60 min and 75 min, respectively. There is a third pipe in the bottom of the cistern to empty it. If all the three pipes are simultaneously opened, then the cistern is full in 50 min. In how much time the third pipe alone can empty the cistern?

110 min
100 min
120 min
90 min

Validate

Solution:

Let the third pipe empty the cistem in

x

min
Part of cistem filled in 1 min when all three pipes are opened simultaneously

=\;{1}/{60}+\;{1}/{75}-\;{1}/{4}

According to the question

\;{1}/{60}+\;{1}/{75}-\;{1}/{x}=\;{1}/{50}

⇒{1}/{x}=\;{1}/{60}+\;{1}/{75}-\;{1}/{50}

⇒{1}/{x}=\;{5+4-6}/{300}

=\;{3}/{300}

⇒1/x=3/300

Thus,

x=\;{300}/{2}=100 {min}

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