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I've got zero that needs to be weighted at 40%

I've then got a whole bunch of numbers let's say the average of 3,2,1,1,1 all weighted at 40%

I've then got another set of numbers, let's say the average of 2,1,1,1 weighted at 20%

Currently what I have is ( 0*.40 + AVG(3,2,1,1,1) *.40 + AVG(2,1,1,1) *0.2 ) / 100

But I guess what i'm trying to ask or figure out is, no matter what the weighting of 0 is, it will always be 0, which i'm not sure is correct or not. Can anyone provide any guidance?

aofe1337
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    0 multiplied by anything is 0. Why, incidentally, are you dividing by 100? – Paul Feb 18 '19 at 22:43
  • Consider by analogy the scenario where you are trying to calculate your overall grade in a course. The final exam is worth 40% of your grade. You have several tests which are worth 40% of your grade as well. Finally, you have homework which is worth 20% of your grade. If you skip your final, of course your overall course grade is going to suffer. – JMoravitz Feb 18 '19 at 22:49
  • trying to use the (w1.x1 + w2.x2 + w3 . x3) / (w1 + w2 + w3) formula – aofe1337 Feb 18 '19 at 22:49
  • "Why are you dividing by 100?" "I'm trying to use the... formula." Note that $0.4 + 0.4 + 0.2$ is equal to $1$, not $100$. – JMoravitz Feb 18 '19 at 22:50

1 Answers1

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You are finding the weighted average of three numbers, $a, b, c$, with weights 40%, 40%, 20% respectively. This is given by $$(0.4 \times a) + (0.4 \times b) + (0.2 \times c).$$

You are taking $a = 0$, $b= \frac{3+2+1+1+1}{5} = \frac{8}{5}$, $c= \frac{2+1+1+1}{4} = \frac{5}{4}$. So the weighted average is $$(0.4 \times 0) + (0.4 \times \frac{8}{5}) + (0.2 \times \frac{5}{4}) = 0.88.$$

Joseph Martin
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