Question 314817
Melody can type a document in 6 hours.
so she can do 1/6 of the job in 1 hour.
..
Mariah can do the job in 9 hours
so she can do the 1/9 of the job in 1 hour.
..
together they can do 1/6  + 1/9 of the job in 1 hour.
=5/18 0f the job
5/18 of the job they do in 1 hour
so for 1 job they take  hou18/5 hours
=3.6 hours