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Continue to ChatX and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last? https://pastmcqs.pk/x-and-y-can-do-a-piece-of-work-in-20-days-and-12-days-respectively-x-started-the-work-alone-and-then-after-4-days-y-joined-him-till-the-completion-of-the-work-how-long-did-the-work-last/