Question

Sally can paint a room in 3 hours while it takes Steve 6 hours to paint the same room how long would it take them to paint the room if they worked together ?

Answer 1

There is a formula:
3 * 6 / (3 +  6) =
18 / 9
= 2 hours

Answer 2

1/3 of an hour (Sally) and 1/6 of an hour (Steve).  

So add the rates: 1/3 + 1/6 = 1/2.  (1/3 is 2/6, and 2/6 + 1/6 = 3/6).  

Since their combined rate is 1/2 of a room in one hour, it takes them two hours to paint the room.  

-Hopes it Helped!