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Math Help - function word problem

  1. #1
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    function word problem

    having trouble with this problem, seems like it should be simple but im just not getting it. when you charge $2 per cup of lemonade you sell 120 cups. when you raise it to $3 per cup you only sell 60. write an equation for the number of cups you sell as a function of the price you charge. denote c for cups and p for price. any helps appreciated. thanks
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  2. #2
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    Quote Originally Posted by brandilee View Post
    having trouble with this problem, seems like it should be simple but im just not getting it. when you charge $2 per cup of lemonade you sell 120 cups. when you raise it to $3 per cup you only sell 60. write an equation for the number of cups you sell as a function of the price you charge. denote c for cups and p for price. any helps appreciated. thanks
    There is no unique solution to this but a straight line can be put through the data as follows:

    Put:

    c = m p + k

    Now when p=2 c=120, so we have:

    120 = 2 m + k

    and when p=3 we have c=60, so we also have:

    60 = 3 m + k

    subtract these, to get: 60 = - m or m=-60, and now put this back into the second
    to get:

    60 = 3(-60) + k

    so k = 240.

    RonL
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  3. #3
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    thanks for you help
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