SOLUTION: Frank can type a report in 5 hours, and James takes 7 hours. How long will it take the two of them typing together? I get 12/35. I know the answer is the inverse, but I don't

Question 274905: Frank can type a report in 5 hours, and James takes 7 hours. How long will it take the two of them typing together?
I get 12/35. I know the answer is the inverse, but I don't know how I should know that. Could you explain how I need to SEE this problem when I read it?
Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
Frank does 1/5 the job in 1 h.
James does 1/7 the job in 1 h.
1/7 + 1/5
=5/35 + 7/35
=12/35 of the job together in 1 h.
or 35/12 hrs to do the job together.
.
Ed
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