Word Problem
posted by Darlene .
Martha can rake the leaves in her yard in 2 hours. Her brother can do the job in 8 hours. How long will it take them to do the job working together?

Together, in an hour, they do (1/2+1/8)=5/8 of the job.
So they will finish the job in (8/5)=1 3/8 hours = 1h22.5 min. 
Emily can rake her lawn in 5 hours. Andrew can rake the same lawn in 8 hours. Rounded to the nearest hour, how long will the job take if they work together?