alleryTwo pipes fill a tank in 20 and 30 hours, and a third empties it in 60 hours. All open, it fills in
A15 hours
B18 hours
C10 hours
D12 hours
Answer & Solution
Correct answer: A. 15 hours
Net rate is 3/60 + 2/60 - 1/60 = 4/60 = 1/15 per hour, so 15 hours.
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