Working together P and Q can do a job is 6 days. Q and R can do the same job in 10 days while P and R can do it in 5 days. How long will it take, if all of them work together to complete the job?
Correct Answer: 42/7 days
Explanation:
(P + Q)'S 1 day's work = 1/6
(Q + R)'s 1 day's work = 1/10
(P + R)'s 1 day's work = 1/5
On adding, 2 (P + Q + R)'s 1 day's work = 1/6 + 1/10 + 1/5 = 7/15
( P + Q + R)'s 1 day's work = 7/30
∴ (P + Q + R)'s can do the entire work in = 30/7 = 42/7 days
