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Algebra Difficulty 3.0 AMC 10/12 Find the answer United Kingdom

It takes 4 hours for a motorboat to travel downstream from X to Y. To return upstream from Y to X it takes the motorboat 6 hours. How many hours would it take a wooden log to be carried from X to Y by the current, assuming it is unhindered by any obstacles? [Assume that the current flows at a constant rate, and that the motorboat moves at a constant speed relative to the water.]

(A) $5$ (B) $10$ (C) $12$ (D) $20$ (E) $24$

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