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Math Help - Proportions

  1. #1
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    Proportions

    Just a couple of simple questions I'm having trouble on.

    6. y is directly proportional to the square of x, and y = 48 when x = 4. What is y when x = 24?

    10. y is inversely proportional to x, and y = 32 when x = 4. what is y when x = 18?

    Thanks.
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  2. #2
    GAMMA Mathematics
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    Quote Originally Posted by PandaPanda View Post
    Just a couple of simple questions I'm having trouble on.

    6. y is directly proportional to the square of x, and y = 48 when x = 4. What is y when x = 24?

    10. y is inversely proportional to x, and y = 32 when x = 4. what is y when x = 18?

    Thanks.
    I'll help you with the first one...

    y=cx^2

    48=16c

    c=3

    y(24)=3*24^2
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  3. #3
    Jen
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    Quote Originally Posted by PandaPanda View Post
    Just a couple of simple questions I'm having trouble on.

    6. y is directly proportional to the square of x, and y = 48 when x = 4. What is y when x = 24?

    10. y is inversely proportional to x, and y = 32 when x = 4. what is y when x = 18?

    Thanks.
    When something is directly proportional it means,
    y=kx where k is some constant.

    Inversly proportional means,
    y=\frac{k}{x}

    so if y is directly proportional to the square of x then,
    y=kx^2

    Then use your values given to solve for K.

    Hope that helps!
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  4. #4
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    Thanks.

    What confused me was there were problems stating "y varies directly/inversely with x" and "y is directly/inversely proportional to x"

    What's the difference?
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  5. #5
    Jen
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    Quote Originally Posted by PandaPanda View Post
    Thanks.

    What confused me was there were problems stating "y varies directly/inversely with x" and "y is directly/inversely proportional to x"

    What's the difference?

    Are you still needing to know the difference, or did I make it clear enough in my last post?
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