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Math Help - 4 questions that I need urgently!!

  1. #1
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    Exclamation 4 questions that I need urgently!!

    Question 1
    A student found that the cost of fixed line phones calls to one location from her home followed a linear model. The cost of a 10 minute call is $1.50 while the cost of a 20 minute call was $2.80.
    a) Graph on the number plane the cost of a call ($) verses the time taken. State and use a scale.
    b) Find the gradient and interpret it in terms of the model.
    c) Find the vertical intercept and interpret its meaning.
    d) Find the equation of the model.
    Question 2

    The speed of sound in dry air at 200 C and 1 atmosphere of pressure is 343 m/s. The speed of sound in steel at 200 C is 5100 m/s.
    a) A measuring device tied to a railway track detects the sound of a train whistle in the steel 2 seconds before it detects the sound in the air.
    How far away was the train when the whistle blew?
    b) The train is travelling at 35 m/s. How far away was the train when the device detected the whistle in the air?

    Question 3

    The points: A(0,0) B(3,4) C(8,0) form a triangle.
    a) Find the exact length of AB.
    b) Find the equation of AB.
    c) Find the perpendicular distance from C to the line AB.
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  2. #2
    Junior Member piglet's Avatar
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    Question 3

    The points: A(0,0) B(3,4) C(8,0) form a triangle.
    a) Find the exact length of AB.
    b) Find the equation of AB.
    c) Find the perpendicular distance from C to the line AB.[/quote]

    a) Use distance formula

    • where  (0,0) = (x1, x2) and  (3,4) =  (y1,y2)

    b) This is simply using the equation of a line formula for two point
     y - y1 = m(x-x1) where  m is the slope of the line between the two points. Im not too sure whether your able to find this so use  m = \frac{y1-y2}{x1-x2} see definations of the points above.

    c)Not too sure about this but im sure someone wiser will tell you. Maybe the following  d = \frac{Ax + By + C}{\sqrt{A^{2}+B^{2}}} where  (x,y) is the point and  Ax + By + C is the line
    Last edited by piglet; April 22nd 2010 at 07:39 AM. Reason: Latex trouble
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  3. #3
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    mr fantastic's Avatar
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    Quote Originally Posted by Jack5 View Post
    Question 1
    A student found that the cost of fixed line phones calls to one location from her home followed a linear model. The cost of a 10 minute call is $1.50 while the cost of a 20 minute call was $2.80.
    a) Graph on the number plane the cost of a call ($) verses the time taken. State and use a scale.
    b) Find the gradient and interpret it in terms of the model.
    c) Find the vertical intercept and interpret its meaning.
    d) Find the equation of the model.
    Question 2

    The speed of sound in dry air at 200 C and 1 atmosphere of pressure is 343 m/s. The speed of sound in steel at 200 C is 5100 m/s.
    a) A measuring device tied to a railway track detects the sound of a train whistle in the steel 2 seconds before it detects the sound in the air.
    How far away was the train when the whistle blew?
    b) The train is travelling at 35 m/s. How far away was the train when the device detected the whistle in the air?

    Question 3

    The points: A(0,0) B(3,4) C(8,0) form a triangle.
    a) Find the exact length of AB.
    b) Find the equation of AB.
    c) Find the perpendicular distance from C to the line AB.
    This looks like work that counts towards your final grade. MHF policy is to not knowingly help with such work - it's meant to be the student's work not someone elses. Pm me if you want to discuss this.

    Thread closed.
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