Q194
ArithmeticTime & Work, Pipes & Cisterns
P, Q and R can do a job in 20, 30 and 60 days respectively. The number of days P can do the job if he is assisted by Q and R every third day is
- a.11 days
- b.15 days
- c.17 days
- d.16 days
Answer: (B) 15 days
In each 3-day cycle P does $\frac{3}{20}$ and Q and R together add $\frac{1}{30} + \frac{1}{60} = \frac{1}{20}$ on the third day, a total of $\frac{1}{5}$. Five such cycles finish the job, which is 15 days. 16 or 17 days overshoot the exact finish.