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Math Help - worded farction problem

  1. #1
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    worded farction problem

    hi

    pls can someone help with this question:

    Mr Smith spent 1/3 of his salary on food and 2/5 of the remainder on transport.

    what fraction of his salary has he left and also ifhe has 600 left find his salary

    Hope you can help with this

    thanks
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  2. #2
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by janvi anish View Post
    hi

    pls can someone help with this question:

    Mr Smith spent 1/3 of his salary on food and 2/5 of the remainder on transport.

    what fraction of his salary has he left and also ifhe has 600 left find his salary

    Hope you can help with this

    thanks
    The trick here is to see that the 2/5 spent on transport is of 2/3 the original amount.

    Let his salary be n

    Food: \frac{n}{3}

    Transport: \frac{2}{5} \times \frac{2}{3}n = \frac{4}{15}n

    Therefore his remaining salary is \left[n(1- \left(\frac{2}{3}+\frac{4}{15}\right)\right] = \frac{n}{15}

    This value is equal to 600: \frac{n}{15} = 600

    n = 9000 (and I'd love to be on that salary!)
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  3. #3
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    hi
    thks for this..but the answer says that he has 2/5 of his salary left and if he had 600 of his salary left then his salrary is 1500..i know that the answer might not always be right but thought this might help.....
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  4. #4
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by janvi anish View Post
    hi
    thks for this..but the answer says that he has 2/5 of his salary left and if he had 600 of his salary left then his salrary is 1500..i know that the answer might not always be right but thought this might help.....
    Nah, I'm probably wrong because 9000 is absurdly high anyway. This time I'll concentrate on what he has left

    OK, let me try again.

    After food he has 2/3 of his salary left.

    After transport he has 3/5 of 2/3 of his salary left.

    This means that overall he has \frac{2}{3} \times \frac{3}{5} = \frac{2}{5} of his salary left (which is the first part answered)

    If this is 600: \frac{2}{5} \times 600 = 1500


    Sorry about that last post >.<
    Last edited by e^(i*pi); February 7th 2010 at 04:26 AM. Reason: typo
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  5. #5
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    thanks very much for this....really appreciate it.....this was my 9 yr old sons h/wk and could not get my head round it!!!
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  6. #6
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by janvi anish View Post
    thanks very much for this....really appreciate it.....this was my 9 yr old sons h/wk and could not get my head round it!!!
    No problem, it threw me initially too XD
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