PMWC Choosing Question
Algebra
Level
pending
3 pipes- A,B&C are supposed to fill up a water reservoir. Pipes A,B&C working together need a total time of 6 hrs. After 2 hours, pipe C stopped working. Two pipes A and B need 7 hours to fill up the water reservoir. How long does it take pipe C to fill up the water reservoir(by itself)?
12
14
21
7
16
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1 solution
A,B&C can fill in 1h : 1/6 part. A,B can fill in 1h : (2/3)/7 = 2/21 part. Let C can fill in 1h : 1/x part. So 1/x + 2/21 = 1/6. 1/x = 3/42. Or x = 14 h