RRB JE Stage I Exam 26 May 2019 Shift 1

Question : 3 of 100

Marks: +1, -0

If P and Q together can do a job in 15 days, Q and R together can do it in 12 days and P and R together can do the same in 20 days, then in how many days will the job be completed, if all the three work together?