Mathematics
Medium
Question
Two pipes A and B can separately fill a cistern in 10 and 15 minutes respectively. A person opens both the pipes together when the cistern should have been was full he finds the waste pipe open. He then closes the waste pipe and in another 4 minutes the cistern was full. In what time can the waste pipe empty the cistern when fill?
A
7 min
B
8 min
✓ Official correct answer
C
9 min
D
10 min
Community credibility
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A
7 min
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B
8 min
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C
9 min
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D
10 min
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