jon can type a report in 9 hours, nick can do the same job in 5 hours. How long would it take to type if they did it together?

Answer 1

1/9 + 1/5 = 14/45 reports per hour is the combined speed

To write one report, 45/14 h is required.

That is 3 3/14 hours, or 3 h 13 min