- A17.5
- B36
- C15
- D20
Step-by-Step Solution
Combined rate = 1/30 + 1/42 = 7/210 + 5/210 = 12/210 tank per hour, so time = 210/12 = 17.5 hours.
Answer: A) 17.5
Working alone, one inlet fills a hostel's overhead tank in 30 hours and another in 42 hours. With both running, how many hours does the tank take to fill?
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