Question 307837
melanie can do a job in 4 hours
so she can do 1/4 of the job in 1 hour

Kim does the same job in 6 hours
So he can do 1/6 job in 1 hour

Together they can do 1/4 + 1/6 of the job in 1 hour

1/4 + 1/6 
= 3+2 / 12
= 5/12 job in one hour

so 1 job they will do together  in 12/5 hours

= 2.4 hours