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Math Help - Linear Functions Help

  1. #1
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    Linear Functions Help

    Could I get some help with this math problem? I'm a complete idiot when it comes to math.

    The cost of water use (in dollars) is a linear function of the amount of water used (in hundreds of cubic feet, HCF), as shown in the figure below. The cost for using 14 HCF of water is $39.40, and the cost for using 28 HCF is $63.90. What is the cost for using 19 HCF of water?


    No clue on how to solve this.

    Please help.
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  2. #2
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    Quote Originally Posted by eraser851 View Post
    Could I get some help with this math problem? I'm a complete idiot when it comes to math.

    The cost of water use (in dollars) is a linear function of the amount of water used (in hundreds of cubic feet, HCF), as shown in the figure below. The cost for using 14 HCF of water is $39.40, and the cost for using 28 HCF is $63.90. What is the cost for using 19 HCF of water?


    No clue on how to solve this.

    Please help.
    I don't think your post is in the right forum...

    Given that data we can make two ordered pairs (14,39.40) and (19,63.90)

    using these two point we can find the slope m.

    m=\frac{63.90-39.40}{19-14}=\frac{24.50}{5}=4.9

    We can then use the slope we just calculated and one of our ordered pairs to find the equation of the line.

    y-39.40=4.9(x-14)

    we can use this equation to find the value for y when x=19.

    Good luck.
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