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Math Help - Fractions Percentages Problem

  1. #1
    eri
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    Fractions Percentages Problem

    Hi,
    Given that
    A:
    Western Australia is 9% of Australias total pop of 17.5 million,
    and
    B:
    City Perth has 6% of Australias total pop of 17.5 million,
    and
    C :
    42% of Australias total pop of 17.5 million live in cities less than 1 mill/rural
    And if Perth is the only city with over 1 mill in Western Australia,
    Question:
    What % percent of the Aussies who live in cities less than 1 mill/rural live in Western Australia??
    The answer could be: 3 % ,7 % ,10 % ,14 % , or 28%)

    Please let me know what the "right" way to do this is.

    My ideas:
    (Pop West Aust) - (Pop Perth) to get the amount of the people in W.A. who live in cities less than 1 mill/rural.
    worked out:
    D:
    (9/100) * 17.5 mill - (6/100) * 17.5 mill = 3/100* 17.5 mill

    Then, if we are looking for how many (%)of the Aussies who live in cities less than1 mill/rural (52% total) live in W.A.

    would we take
    D/C that is, (people in W.A who live in cities<1 mill/rural) divided by (Australias total pop of people in cities<1 mill/rural)

    or

    just take D/17.5 mill ? I think this latter would actually be the % of total Aussie population who live in WA (minus Perth), not the % of the Aussies who live in cities<1 mill/rural

    So I get 7.1%
    Tell me if I am wrong....
    thanx folks!
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  2. #2
    MHF Contributor
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    Let me re-do my reply.

    "42% of Australias total pop of 17.5 million live in cities less than 1 mill/rural"

    "Western Australia is 9% of Australias total pop of 17.5 million,"
    "City Perth has 6% of Australias total pop of 17.5 million,"
    "And if Perth is the only city with over 1 mill in Western Australia,"
    "What % percent of the Aussies who live in cities less than 1 mill/rural live in Western Australia??"

    So, the West Australians that are not in Perth are (9% -6%) = 3% of all Australians.
    Let x% of all Australians be those Australians in West Australia that live in cities with less than a million/rural.
    By proportion,
    42% of 100% Australians = x% of 3% Australians
    0.42 = 0.03x
    x = 0.42 / 0.03 = 14% ----------answer.
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  3. #3
    eri
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    Clarification? trying to understand

    Quote Originally Posted by ticbol View Post
    Let me re-do my reply.

    "42% of Australias total pop of 17.5 million live in cities less than 1 mill/rural"

    "Western Australia is 9% of Australias total pop of 17.5 million,"
    "City Perth has 6% of Australias total pop of 17.5 million,"
    "And if Perth is the only city with over 1 mill in Western Australia,"
    "What % percent of the Aussies who live in cities less than 1 mill/rural live in Western Australia??"

    So, the West Australians that are not in Perth are (9% -6%) = 3% of all Australians.
    Let x% of all Australians be those Australians in West Australia that live in cities with less than a million/rural.
    By proportion,
    42% of 100% Australians = x% of 3% Australians
    0.42 = 0.03x
    x = 0.42 / 0.03 = 14% ----------answer.
    I thought that the rest of the Aussies in West Austr. that remain when you subtract Perthians are the population living in cities< 1 mill/rural.
    So the 3% would all be living in cities< 1 mill/rural
    the question is what % of aussies living in cities< 1 mill/rural live in W.A.

    Ideas?
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  4. #4
    eri
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    I see I made an error in the last part of my calculations--52 instead of 42!
    ok i tried with 42...
    % 45/100*17.5 mill = 3/100*17.5 mill
    This is where i get 7%

    please let me know if you think i'm doign the correct approach, or if the 1st responder is right in that approach. i don't understand that logic too much.

    thanks
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  5. #5
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    Let me do it again, by the numbers this time.

    Those West Australians who live in cities with less than 1 million people are 3% of 17.5M.
    So, those are 0.03(17.5) = 0.525 million

    Those Australians who live in cities with less than 1 million people are 42% of 17.5M
    So, those are 0.42(17.5) = 7.35 millions.

    What percent of 7.35 millions is 0.525 million?
    That will be 0.525 / 7.35 = 0.07143.
    That, then, is 7.143%

    Umm, so that is why I was uncomfortable with my "by proportion" in my first reply. It was not in the form of "ratio = ratio".
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