Dave paints a fence in 4 hours while Sara paints the same fence in 2 hours. If they work together, h

Discussion in 'Calculator Requests' started by math_celebrity, Nov 21, 2022.

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  1. math_celebrity

    math_celebrity Administrator Staff Member

    Dave paints a fence in 4 hours while Sara paints the same fence in 2 hours. If they work together, how long will it take them to paint the fence?

    Set up unit rates:
    • Dave paints 1/4 of the fence in 1 hour
    • Sara will paint 1/2 of the fence in 1 hour
    So together, they paint 1/2 + 1/4 = 2/4 + 14 = 3/4 of the fence in one hour.
    1 hour = 60 minutes, so we set up a proportion of time to minutes where m is the time in minutes needed to complete 1 full fence:
    3/4/60 = 1/m
    3/240 = 1/m

    Typing this proportion in our math engine, we get:
    m = 80 minutes

    80 minutes is also 1 hour and 20 minutes.
     

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