Problem Solving

Working alone, printers X, Y and Z can do a certain 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 X to do the job, working alone at its rate, to the time it takes printer Y and Z to the the job, working together at their individual rates?

(A) 4/11
(B) 1/2
(C) 15/22
(D) 22/15
(E) 11/4

X can complete the work in 12 hrs.
Y + Z together can complete the work in (15 * 18)/33 hrs.
Ratio of time X/ Ratio of time(Y + Z)

= 12/[(15*18)/33] = 22/15.

What is the OA?

Correct! OA is D

For more explanation of how to approach this type of problem see this combined work rate problem tutorial.