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Math Help - puzzled with percentages

  1. #1
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    Unhappy puzzled with percentages

    hi everyone.. i have a simple but puzzling problem that i came across. just read the example:

    say you have high-low-mid situation for say expectations for products..

    so, you ll have :
    Low:10
    mid:20
    high:30

    total=60


    Now, say we want to check what the 30% would be of that total (simple answer..) = 18

    the problem begins now..:
    say we assign some percentages for this low-mid-high averaging to 30%..just to check

    so, say aagain that we assign further that:
    low: 10% of the 10 above (=1)
    mid:30% of the 20 (=6)
    high:50% of 30..(=15)

    the average of these percentages is 30% but the result is 22!!..
    i can see that the last 30% does not represent the 30% of the total directly...but then again..it s 30%...well once again i am puzzled to explain it can u please tell me the reason?
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  2. #2
    Bar0n janvdl's Avatar
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    You used 30% on all the numbers in your first calculation, not an AVERAGE of 30%.

    You did the first one this way:

     ( \frac{30}{100} \times 10) + ( \frac{30}{100} \times 20) + ( \frac{30}{100} \times 30) = 18

    And the second one this way:

     ( \frac{10}{100} \times 10) + ( \frac{30}{100} \times 20) + ( \frac{50}{100} \times 30) = 22


    And therefore you will get two very different answers...
    Last edited by janvdl; October 31st 2007 at 04:11 AM.
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  3. #3
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    thanks.. i still got a little confused at the beginning but i figured out the whole thing with yr clue.
    yes..indeed..that is how i first thought abt it,by using weight for each value.. but the wording trick is that since the first calculation represents 30% of the values...and then the second represents 30% of the values too...why not match!?i think i m getting confused again!lol
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  4. #4
    Bar0n janvdl's Avatar
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    Quote Originally Posted by tsatsos007 View Post
    thanks.. i still got a little confused at the beginning but i figured out the whole thing with yr clue.
    You'll see I edited my post, check if it makes a little more sense now...
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  5. #5
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    i think i found the explanation in words..it IS that it represents 30% in both cases..yet with different weighting for the values!right?
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  6. #6
    Bar0n janvdl's Avatar
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    Quote Originally Posted by tsatsos007 View Post
    i think i found the explanation in words..it IS that it represents 30% in both cases..yet with different weighting for the values!right?
    No, my logic says it's not 30%.
    It's 30% in the FIRST case yes.
    In the second it's 10% , 30% , 50%.
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  7. #7
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    why... since 10+30+50=90...then, 90/3=30..so, 30%..
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  8. #8
    Bar0n janvdl's Avatar
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    Quote Originally Posted by tsatsos007 View Post
    why... since 10+30+50=90...then, 90/3=30..so, 30%..
    It just doesn't work that way. In the first one you applied 30% to every value.

    In the second one you applied different percentages to every value. It just won't work. It's maths!
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  9. #9
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    ;-)
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