Correct Answer: Option D
Part filled in 5 min = 5 * (1/12 + 1/15) = 5 * 9/60 = 3/4 Part emptied in 1 min when all the pipes are opened = 1/6 - (1/12 + 1/15) = 1/60 Now, 1/60 part is emptied in 1min ∴ 3/4 part will be emptied in 60 * 3/4 = 45 min
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