posted by Lucy .
Thomas 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 it they work together?
With two of them working together, then their times will be cut in half. Thomas can do it in 2 hours, while Julia does it in 3 hours.
(2 + 3)/ 2 = 2 1/2 hours
Their combined rate of doing the rob is
1/4 job/h + 1/6 job/h = 5/12 job/h
5/12 job/h * T (hr) = 1 job
T = 12/5 = 2 2/5 hours
Thanks, again -- DrWLS. You're absolutely right -- and I was wrong.
Maybe they stood around chatting for the additional 6 minutes? <G>