Q. Two pipes, when working one at a time can fill a cistern in 2 hrs and 3 hrs, respectively while a third pipe can drain the cistern empty in 6 hrs. All the three pipes were opened together when the cistern was 1/6 full. How long will it take for the cistern to be completely full?
A) 1 hour 30 min
B) 1 hour
C) 1 hour 15 min
D) 1 hour 20 min
✔ Correct Answer: 1 hour 15 min
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