Working alone, Printers X, Y, and Z can do a certain printing job, consisting of a large number of pages, in 12, 20, and 20 hours, respectively. What is the ratio of the time it takes Printer X to do the job, working alone at its rate, to the time it takes Printers Y and Z to do the job, working together at their individual rates? Answers.
A) 4/11	B) 1/2	C) 15/22	D) 10/1	E) 11/4
P1 takes 12 hrs   Rate for P2P3 together = 1/20 + 1/20 = 1/10   Therefore they take 10   Ratio = 10/1= 
<gadget id="calculator">10/1</gadget>
<output>10</output>
10/1
<result>D</result>
Working alone, Printers X, Y, and Z can do a certain printing job, consisting of a large number of pages, in 12, 20, and 20 hours, respectively. What is the ratio of the time it takes Printer X to do the job, working alone at its rate, to the time it takes Printers Y and Z to do the job, working together at their individual rates?