Answer:
Explanation:
Comment
Though it is easier to use the origin as one of the points to find the rise over the run, doing the question the more general way will help you with lines that do not go through the origin.
So pick any other two points.
P1(6 , 0.60)
P2(8 , 1.20)
Rise / Run = (y2 - y1)/(x2 - x1)
y2 = 1.20
y1 = 0.90
x2 = 8
x1 = 6
Rise over Run = (1.2 - 0.9) / (8 - 6)
Rise over run = 0.3 / 2
Technically stated in language, this is the answer. For every 2 pencils the cost goes up 0.3 cents. Carpenters would say it this way.
However in physics it can also be expressed as 0.15 dollars per pencil which is the cost per pencil.
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Just to show that you will get the same answer using the origin you can do it this way.
y2 = 0.6
y1 = 0
x2 = 4
x1 = 0
rise over run = (0.6 - 0)/ (4 - 0) = 0.6/4 = 0.15 / 1
