Two inlet pipes A and B can fill a basin in 20 and 30 minutes individually. Operating both pipes concurrently, how much duration is needed to fill the basin?
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Answer: A. 12 min
Explanation
Inlet pipes A and B possess individual work rates of one twentieth and one thirtieth per minute. Adding one twentieth and one thirtieth gives a combined rate of five over sixty or one twelfth per minute. Taking the reciprocal of the combined work rate reveals that both pipes fill the basin in twelve minutes. The combined rate of two inlet pipes operating together is the sum of their individual unit rates. Fractions representing work rates must share a common denominator before they can be added. The total time to complete filling a basin is the inverse of the combined flow rate fraction.
Option b overestimates the required time by failing to sum the concurrent flow rates correctly. Option c corresponds to an incorrect rate addition that yields a much slower fill time. Option d represents the fill time of the slower pipe operating entirely on its own.
- Subject
- Mathematics
- Category
- Mathematics
- Topic
- —
- Difficulty
- medium
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