SOLUTION: A librarian arranges books in 3 hours. A volunteer student can do the same job in 5 hours. If they work together for 1 hour and the student leaves then how much longer does the lib

Question 768510: A librarian arranges books in 3 hours. A volunteer student can do the same job in 5 hours. If they work together for 1 hour and the student leaves then how much longer does the librarian have to work?
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
The task of arranging the books takes hours of work by the librarian.
That means that the libraraian completes of the job in 1 hour.
That is the librarians speed/rate of work.
The volunteer student is slower.
He/she needs 5 hours to do the same work, and that means that his/her speed/rate of work is
of the task pe hour.
Working together for 1 hour, they complete
of the work of arranging the books.
That means that the fraction of the job remaining is of the job.
That much work is left for the librarian to finish alone.
At a rate of of the job per hour, it will take the librarian

.
Calculating it as hours and minutes:

and

The librarian will have to work 1 hour and 24 minutes longer after the volunteer student leaves.
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