SOLUTION: Suppose that it takes John 9 hours to paint a barn if he works alone and it takes Carl 6 hours to paint the same barn if he works alone. How long will it take them to paint the bar

Algebra ->  Rate-of-work-word-problems -> SOLUTION: Suppose that it takes John 9 hours to paint a barn if he works alone and it takes Carl 6 hours to paint the same barn if he works alone. How long will it take them to paint the bar      Log On


   

Question 1057920: Suppose that it takes John 9 hours to paint a barn if he works alone and it takes Carl 6 hours to paint the same barn if he works alone. How long will it take them to paint the barn, in hours, if they work together?
Answer by jorel555(1290) About Me  (Show Source):
You can put this solution on YOUR website!
If John takes 9 hours to paint a barn, then he does 1/9th of a barn per hour. Similarly, Carl does 1/6th of a barn per hour. Together, they can do 1/9 + 1/6 , or 5/18ths of a barn per hour. Then 1 barn takes 1/(5/18), or 18/5ths hours with the two of them working together. ☺☺☺☺