- A7 h
- B5 h
- C6 h
- D8 h
Step-by-Step Solution
First 2 h: . Then ; takes 5 h. Total 7 h. (5 h is only the second stage.)
Answer: A) 7 h
Pipes P, Q and R fill a tank in 10, 15 and 30 hours. P is open throughout, Q is closed after 2 hours, and R is opened only when Q closes. How long does the empty tank take to fill?
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