X and Y can do a piece of work in 15 days. Y and Z together can do it in 9 days. If Z is twice as good a workman as X, then find in how many days can Y alone does the work?
Answer & explanation
Correct answer: option 4
Z is twice as good a workman as X
i.e. Z : X
2 : 1
Let 4 : 2
as X + Y = 3R → Y = 3R - 2R = R
Z + Y = 5R → Y = 5R - 4R = R
X : Y : Z
2 : 1 : 4
Total work = Efficiency × Number of days
Time taken by Y to do work = \(\frac{45R}{R}\) = 45 days