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Math Help - Finding Slope from Equation/Graph

  1. #1
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    Lightbulb Finding Slope from Equation/Graph

    Alright here is what I am working on:

    Finding Slope from Equation/Graph-screen-shot-2013-08-30-10.53.18-am.png

    Is my graph correct because for some reason I keep getting the wrong answer for the slope. I don't know why I am having so much difficulty. (I keep getting -1 for slope...)
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  2. #2
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    Re: Finding Slope from Equation/Graph

    Quote Originally Posted by michellederz View Post
    Is my graph correct because for some reason I keep getting the wrong answer for the slope.
    Your graph corresponds to P = 50 - Q, while the correct relationship is P = 10 - Q/5.

    Now, the question about slope is devious because the two axes have different scales. If the scales were the same, the slope would be equal to the coefficient of the independent variable, which is Q here, i.e., -1/5. Maybe this is what the question is asking. If you need the slope of the actual graph of P(Q) in these axes, then note that one square along the Q axis represents 10 units while one square along the P axis represents 5 units. Suppose the square side length is 1cm. If Q increases by 10, i.e., 1cm, then P decreases by -2 (since Q is multiplies by -1/5), i.e., -2/5cm. Therefore, the slope of the graph is -2/5cm / 1cm = -2/5..
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  3. #3
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    Re: Finding Slope from Equation/Graph

    Quote Originally Posted by emakarov View Post
    Your graph corresponds to P = 50 - Q, while the correct relationship is P = 10 - Q/5.

    Now, the question about slope is devious because the two axes have different scales. If the scales were the same, the slope would be equal to the coefficient of the independent variable, which is Q here, i.e., -1/5. Maybe this is what the question is asking. If you need the slope of the actual graph of P(Q) in these axes, then note that one square along the Q axis represents 10 units while one square along the P axis represents 5 units. Suppose the square side length is 1cm. If Q increases by 10, i.e., 1cm, then P decreases by -2 (since Q is multiplies by -1/5), i.e., -2/5cm. Therefore, the slope of the graph is -2/5cm / 1cm = -2/5..
    So then the graph would be P=10-Q/5 & not P=10-Q5 as it states above the line?
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  4. #4
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    Re: Finding Slope from Equation/Graph

    Quote Originally Posted by michellederz View Post
    So then the graph would be P=10-Q/5 & not P=10-Q5 as it states above the line?
    Which line and where does it say P=10-Q5? The answer to the multiple-choice question in the attachment is correct: P = 10 - (1/5)Q, which is the same as P = 10 - Q/5.
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