Y is thrice as efficient as Z who is half as efficient as X,X,Y and Z can complete a job in 25 days. Find the time in which X and Y can complete it (in days)

Options

A. 30
B. 36
C. 40
D. 45

Explanation

Let the time in which X,Y and Z can complete the job be x days, y days and z days respectively.
`(1)/(y)=3((1)/(z)) and (1)/(z)=(1)/(2)=((1)/(x))`
`:. y=(z)/(3) and x=(z)/(3)`
`(1)/(x)+(1)/(y)+(1)/(x)=(1)/(25)`
`(2)/(z)+(3)/(z)+(1)/(z)=(1)/(25)=rArrz=150`
`:. y50 an x=75`
X and Y can complete it in `((75)(50))/(75+50)` days =30 days