Kelly took 4 hours to paint a room. Richard took 8 hours to paint an identical room. If both of them worked together, how long would they take to paint the room?
Here's an easy way to do this
1/4 + 1/8 =
2/8 + 1/8 =
Take the reciprocal of this fraction = 8/3 = hrs to paint the room if they work together = 2 + 2/3 hrs =
2hrs 40 min