15. A manager plans to distribute journals to his staff at the end of the year.
He sends an email to a printing firm and obtains the following quotation:
Quotation for journals
. $240 for 10 journals
$330 for 15 journals
• $420 for 20 journals
The more you order, the less you pay!
.
(i) By letting x represent the number of journals and Sy represent the cost, write down three pairs of
coordinates from the information provided.
[1]
(ii) Using a scale of 1 cm to represent 2 journals, draw a horizontal x-axis for values of x from 0 to 20.
Using a scale of 2 cm to represent $100, draw a vertical y-axis for values of y from $0 to $500.
Plot the points in part (i) and join them with a straight line.
(iii) Extend the line in part (ii) such that it intersects the y-axis.
Explain the significance of the y-intercept of the graph.
[1]
(iv) The manager is not sure whether the caption "The more you order, the less you pay!" is a true statement.
[2]
Explain clearly whether you agree with the caption. Show calculations to support your answer.
[3]