Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Dividing a number w/uncert by a number w/o uncert

  1. Sep 25, 2011 #1
    1. The problem statement, all variables and given/known data
    If I have a number with an uncertainty and I want to divide it by a number without an uncertainty (ex. if it's just a constant, like pi), what do I do with the uncertainty? Is it ok to just divide the uncertainty by that number?

    ex. (4.05 +/- 0.3) / 3

    Do I divide the 0.3 uncertainty by 3, and that would be my uncertainty for the final answer, or do I have to do percentage uncertainties?


    2. Relevant equations
    N/A


    3. The attempt at a solution
    Intuition tells me it's the first, but I'm not sure.
     
  2. jcsd
  3. Sep 25, 2011 #2
    (4.05 +/- 0.3) / 3 = (4.08 to 4.02) / 3 = 1.36 to 1.34 = 1.35 +/- 0.1

    So I think you are right.
     
  4. Sep 26, 2011 #3
    Yes, the uncertainty is also mulitplied (or divided, in this case) by the constant.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook