- A14
- B31.5
- C21
- D12
Step-by-Step Solution
Combined rate = 1/21 + 1/42 = 2/42 + 1/42 = 3/42 = 1/14 of the tank per hour, so 14 hours.
Answer: A) 14
Two taps fill a school's water tank in 21 hours and 42 hours respectively. Opened together, in how many hours will they fill it?
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