- A120 hours
- B115 hours
- C114 hours
- D60 hours
Step-by-Step Solution
Each 2-hour pair adds . After 57 pairs (114 h) the tank is full; the inlet's next hour adds , exactly enough. So 115 hours.
Answer: B) 115 hours
An inlet fills a tank in 20 hours and an outlet empties it in 30 hours. They are opened alternately for 1 hour each, inlet first, on an empty tank. After how many hours is it full?
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