Working alone, printers P1, P2, and P3 can do a certain printing job, consisting of a large number of pages, in 12, 15, and 18 hours, respectively. What is the ratio of the time it takes printer P1 to do the job, working alone at its rate, to the time it takes printers P2 and P3 to do the job, working together at their individual rates?
P1 takes 12 hrs
Rate for P2 & P3 together = 1/15 + 1/18 = 11/90
Therefore they take 90/11
Ratio = 22/15 = D
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