posted by jessica .
Tomas can do a job in 4 hours. julia can do the same job in 6 hours. how many hours will it take the two of them to do the job if they worked together?
In 24 hours, they can do 10 jobs (numberjobs=24/4 + 24/6)
so it takes 2.4 hours (24/10) hours per job with both of them working.