P and Q can finish a work in 15 and 10 days respectively. Q starts the work and leaves it after 5 days. The number of days in which P can complete the work is :
Explanation:
P's 1 day's work = 1/15
Q's 1 day's work = 1/10
Q's 5 day's work = 5/10 = 1/2
So, P can do the remaining work in 15/2 days.
∴ Required days = 7 ½ days