Kyle can paint a fence in 10 hours. Niall can paint the same fence in 8 hours. If they finished 27/40 of the job by working together, how long did they work together?

Answer 1

1/K + 1/N = 1/T

1/10 + 1/8 = 1/T

multiply both sides by 40T

4T +5T = 40

9T = 40

They can do it together in 40/9 hours = 4 4/9 = 4.444... hours

27/40 of 40/9 = 3 hours