Question

A telephone company charges a fixed monthly rate plus a rate per minute of usage. The company charges $155 for 100 minutes of usage and $245 for 200 minutes of usage. An equation can be written to show the relationship between the total minutes used (x) and the total monthly charges (y). Which of the following best describes the steps to draw the graph of y against x?

Draw a graph which joins the points (155, 100) and (245, 200) and has a slope = 0.9
Draw a graph which joins the points (155, 100) and (245, 200) and has a slope = 1.1
Draw a graph which joins the points (100, 155) and (200, 245) and has a slope = 1.1
Draw a graph which joins the points (100, 155) and (200, 245) and has a slope = 0.9

Answer 1

Just took the exam and the answer would be d :)

Answer 2

The solution is "Draw a graph which joins the points (100, 155) and (200, 245) and has a slope = 0.9"

the points are (minute,cost) pairs like the assignment states
the slope is the difference of both costs (90) divided by the minute difference (100)
so k=90/100=0.9

so the last option