Question

If Sally can paint a house in 4 hours, and John can paint the same house in 6 hour, how long will it take for both of them to paint the house together?
I did not get the answer to this problem, so if you could please give me some solutions.

Answer 1

Sally can paint the house in 4 hours
The rate at which he  can paint the house is 1/4 per hour
John can paint the house in 5 hours
                       The rate is 1/5 hours
Together the rate is 1/4+1/5=9/20
So they can paint the house in 1/(9/20)=20/9 hours =2.22hrs