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A pipe fills a tank in 6 hrs; another empties it in 9 hrs. Both open together, when does the tank fill?
Answer & Solution
Correct answer: D.
1. Filling rate: 1/6. Emptying rate: −1/9.
2. Net rate: 1/6 − 1/9 = 3/18 − 2/18 = 1/18 per hour.
3. Time = 18 hours.
_Source: TSICET 2024 PYQ Q.84 (Shift 1, Pipes and Cisterns)_