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Homework Help: Propagation error in finding the perimeter and area, please help.

  1. Sep 5, 2011 #1
    1. The problem statement, all variables and given/known data
    I want to measure the size of my back yard. I estimate that I can measure the length and width of the yard using a tape measure to an accuracy of 0.05m. I find that the length of the yard is 8.6 m and the width is 7 m.

    Calculate the perimeter of the yard and its error
    Now calculate the area of the yard and its error

    2. Relevant equations
    s=square root(changeA)^2+(changeB)^2)

    3. The attempt at a solution
    I calculated the perimeter and got 31.4m. i cant figure out how to get the error in the perimeter. I thought it would be 8.55(2)+6.95(2) =31.0 -31.4=.4 but its not correct
  2. jcsd
  3. Sep 5, 2011 #2


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    Gold Member

    You say your accuracy is 0.05m.

    Then the length is 8.60 m. the error in measurement is 0.05m
    The width is 7.00m with a measurement error of 0.05m
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