SOLUTION: A painter can paint a building in 15 days and a co-worker can do the same job in 10 days. If the first painter starts and 3 days later the co-worker joins in to help finish the job

Question 1115558: A painter can paint a building in 15 days and a co-worker can do the same job in 10 days. If the first painter starts and 3 days later the co-worker joins in to help finish the job, how many days does it take to paint the building?
Answer by ikleyn(52783) (Show Source): You can put this solution on YOUR website!
.

1.  From the condition, the first painter makes    of the job per day.

    The second makes   of the job per day.


    Hence, working together, they make   =  =  =   of the job per day.

    It is their combined rate of work.



2.  Working for 3 days, the first painter made   =  of the job.

    Hence,   of the job remained.



3.  Thus the two, working together, must complete   of the job.

    Since their combined rate of work is   of the whole work per day,
    it will take them    =  =  of the day =  days = 4.8 days.

Answer. The schedule is this: first painter works 3 days, and then the two work together for 4.8 days.

Solved.

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