Practice Test Discussion


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?

[CAT level]

  • Explanation

    Let us assume the third pipe empties the cistern in x min.

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


    According to the question,

    150=160+175-1x1x=5+4-6300=3300x=3003=100 minutes

    Hence option B is correct. 

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    Pipes and cisterns

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