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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.