Anna paints a fence in 4 hours wile her brother paints it in 5 hours. If they work together, how lon

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Anna paints a fence in 4 hours wile her brother paints it in 5 hours. If they work together, how long will it take them to paint the fence?

Set up unit rates per hour:

• Anna paints 1/4 of a fence per hour
• Brother paints 1/5 of a fence per hour
• Combined, they paint 1/4 + 1/5 = 9/20 of a fence per hour

Setup a proportion of time to hours where h is the number of hours needed to paint the fence
9/20 of a fence the first hour
18/20 of a fence the second hour
2/20 is left. Each 1/20 of the fence takes 60/9 = 6 & 2/3 minutes
6 & 2/3 minutes * 2 = 13 & 1/3 minutes

Final time is:
2 hours and 13 & 1/3 minutes