Shamus can paint the barn in 6 hours, and Ishmael can paint the barn in 7 hours. How long will it take them to paint the barn together?

Question

Shamus can paint the barn in 6 hours, and Ishmael can paint the barn in 7 hours. How long will it take them to paint the barn together?

Answer 1

In x hours Shamus paints x/6 of the barn

In x hours Ishamel paints x/7 of the barn

 

x/6 + x/7 = 1

7x + 6x = 42      multiply both sides by LCD, 42

13x =42

 

How many hours does it take them?