Question

a cistern can be filled by two pipes in 20 and 30 minutes respectively but a waste pipe can empty it in an hour both the suppply pipes were opened together to fill the empty cistern,but by mistake the waste pipe was closed,if the cistern is filled in 14 min.
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Answer 1

Your answer is in the attachment. Hope this helps you. mark as brain list . Your question was not understood by me. But I did. Up to how much I could understand. Next time be sure to post full question.