1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

On calculation weighted average of two positive numbers

  1. Dec 2, 2013 #1
    1. The problem statement, all variables and given/known data
    Given two positive numbers calculate their weighted average(Note: This is not actually a homework question, but silly me have doubts, so I put it in this category)


    2. Relevant equations

    Two given positive numbers a,b. No separate weights are available to weigh each numbers

    3. The attempt at a solution
    Can I do the following by considering the weight as the number as a fraction of the sum of two numbers?

    weighted average = a*(a/a+b) + b*(b/a+b) =( a^2 + b^2) /(a+b)
    So, for two numbers 9 and 11, the arithmetic mean will be 10, and weighted mean will be,
    9*(9/20) + 11 *(11/20) = 9*0.45 + 11 * 0.55 = 10.1

    Thank you
     
  2. jcsd
  3. Dec 2, 2013 #2

    Mark44

    Staff: Mentor

    Looks OK to me, but a more realistic example would be, say test scores that have different weights. For example, suppose a class is graded on the results of a midterm (weight = 35%) and a final exam (weight = 65%). If a student received a midterm grade of 78 points and a final exam grade of 90 points, what would be the weighted average of these two scores?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted