# 4 questions that I need urgently!!

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#### Jack5

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. #### piglet 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 $$\displaystyle (0,0) = (x1, x2)$$ and $$\displaystyle (3,4) = (y1,y2)$$ b) This is simply using the equation of a line formula for two point $$\displaystyle y - y1 = m(x-x1)$$ where $$\displaystyle m$$ is the slope of the line between the two points. Im not too sure whether your able to find this so use $$\displaystyle m = \frac{y1-y2}{x1-x2}$$ see definations of the points above. c)Not too sure about this but im sure someone wiser will tell you. Maybe the following $$\displaystyle d = \frac{Ax + By + C}{\sqrt{A^{2}+B^{2}}}$$ where $$\displaystyle (x,y)$$ is the point and $$\displaystyle Ax + By + C$$ is the line Last edited: #### mr fantastic MHF Hall of Fame 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.