Question 1198854
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Tutor @ikleyn has provided a typical formal algebraic solution.<br>
Without algebra, it might make sense to you that, since the two together take half as much time as Quiboy alone, it would also take Rod the same 6 hours to do the job alone.<br>
If it is hard for you to see that solution using logical reasoning, here is another method for solving the problem.<br>
In 6 hours, Quiboy can do the job alone.<br>
In those same 6 hours, the two of them together could do the job twice, because it takes them 3 hours to do the job once.<br>
So in 6 hours Quiboy could do the job 1 time, while in 6 hours the two together could do the job twice; that means in those same 6 hours Rod could do the job once.<br>
ANSWER: Rod alone would take 6 hours to clean the barn alone.<br>