1.

A vistern can be filled by two supply pipes in 20 minutes and 30 minutes respectively. But a waste pipe can empty it in an hour. Both the spply pipes were opened together to fill the empty cistern, but by mistake the waste pipe was also open. Some timelaterthe waste pipe was closed. How much later was the waste pipe closed, if the cistern is filled in 14 minutes?

Answer»

6 minutes
8 minutes
10 minutes
12 minutes

Answer :C


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