- A9 h
- B7 h
- C6 h
- D12 h
Step-by-Step Solution
In 12ths: start at 6; A adds 3, B removes 2, so each 2-hour round gains 1. After 3 rounds (6 h): 9; A's next hour brings it to 12. Total 7 h. (12 h treats the tank as empty.)
Answer: B) 7 h
The tank in the figure is half full. Pipes A and B are opened alternately for one hour each, starting with A. After how many hours is the tank first full?
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