Two pipes A and B fill a water reservoir in 4 and 5 hours respectively. Operating them sequentially for one hour each on an alternating basis, what duration is required to fill the container?
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Answer: B. 4 hrs 24 min
Explanation
Pipe A fills one quarter of the tank every single hour. Pipe B fills one fifth of the tank during its operating hour. Alternating operation fills nine twentieths of the tank every two hours. Work rates of individual pipes are calculated as the reciprocal of total time. Sequential operations mean only one pipe actively fills the container at any moment. Remaining fractions of work require proportional time based on the active pipe rate.
This mathematical puzzle models filling tasks with alternating independent industrial water pumps. Proper scheduling of multi-source filling systems prevents overflow and equipment burnout. Engineers use similar pacing calculations for intermittent chemical batch processing operations. Option A underestimates the total time required by ignoring the fractional remainder step. Option C overestimates the total time because the tank is already full before five hours. Option D fails to account for the final partial hour needed to finish filling.
- Subject
- Mathematics
- Category
- Mathematics
- Topic
- —
- Difficulty
- medium
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