Mathematics
NULL
Medium
Question
Taps A, B and C fill a tank in 12, 15 and 20 hours. If A stays open and B and C open for one hour each alternately, when will the tank be full?
A
6 hours
B
6 2/3 hours
C
7 hours
✓ Official correct answer
D
7 1/2 hours
Community credibility
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A
6 hours
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B
6 2/3 hours
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C
7 hours
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D
7 1/2 hours
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Explanation
In 2 hours (A+B then A+C): 17/60 of the tank. After 6 hours: 51/60. The remaining 9/60 is filled in the next hour by A+B. Total = 7 hours.