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Homework Help: Dealing with uncertainties

  1. Feb 26, 2009 #1
    1. The problem statement, all variables and given/known data
    When doing operations with numbers with uncertainties, if the significant figures of the resultant number's uncertainty is lower the significant figures of the resultant number, how should I show the resultant uncertainty. For example,


    2. Relevant equations
    if you do the operation 5.40+-0.10 / 90.00+-0.05 , the result is
    0.06+-0.001


    3. The attempt at a solution
    the solution must either be
    0.06 +- 0.00

    or

    0.06 +- 0.01x(10^(-1))

    since the number of the significant numbers should be equal. so which one is it?
     
  2. jcsd
  3. Feb 26, 2009 #2

    HallsofIvy

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    Science Advisor




    That "5.40+-0.10" is a little misleading. Although 5.40 is written as if it had 3 significant figures, that +-0.10 says that is is uncertain in the tenths place and so only has 2 significant figures. One way to do this is to calculate the largest possible value: 5.5/90.05= 0.6111 and smallest value: 5.3/89.95= 0.05886 That can be written as 0.06+-0.2.
     
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