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?

Answer 1

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

Answer 2

Not quite.

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

Answer 3

Thanks, again -- DrWLS. You're absolutely right -- and I was wrong.

Answer 4

Maybe they stood around chatting for the additional 6 minutes? <G>