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A simple qestion

  1. Dec 22, 2014 #1
    Three of four numbers have a sum of 22. If the average of
    the four numbers is 8, what is the fourth number?
    A. 4
    B. 6
    C. 8
    D. 10
  2. jcsd
  3. Dec 22, 2014 #2
    apply the average rule:

    the sum of all the numbers / the number of the numbers

    you would get only one unknown to find.
  4. Dec 22, 2014 #3
    I'm not given the other 3 numbers. I think I'm misinterpreting what you are saying sum/amount of numbers or sum/each number totaled up. 22/4=5.5 evenly distributed. I'm also running into an issue also one of the numbers doesn't necessarily have to be 8 the 4 numbers average is 8.

    oh wait 3 of 4 numbers have a sum of eight. 6,7,, and 9=22 so the 4th number has to be 8. but 22/3=7.3 I mean visually it makes sense but mathematically I'm not getting the answer.
    Last edited: Dec 22, 2014
  5. Dec 22, 2014 #4


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    Homework Helper

    The average of the four numbers is 8. What is the sum of the four number?
  6. Dec 22, 2014 #5
    Would that be (22+x)/4=8 ok I got 10. Thanks. I just had to think a bit more straighter. :)
  7. Dec 22, 2014 #6


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    Homework Helper

    Correct! You could have done it without writing an equation.. if the average of N number is A, the sum of them is NA. The average of 4 number is 8, then the sum of them is 32. .But the sum of three of them is 22, and adding the fourth yields 32...
  8. Dec 22, 2014 #7
    I don't know, I think I work better by writing down equations or just writing everything down.
  9. Dec 22, 2014 #8


    Staff: Mentor

    Please use the template and show some effort.
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