- A15 h
- B18 h
- C12 h
- D9 h
Step-by-Step Solution
Thirds at 9 h per tank: first third 3 h; middle third at : 6 h; last third 3 h. Total 12 h. (18 h has the leak all the way.)
Answer: C) 12 h
A tap fills a cistern in 9 hours. When the cistern is one-third full, a leak starts that alone would empty the full cistern in 18 hours; when it is two-thirds full, the leak is repaired. How long does the filling take altogether?
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