Find the constant of proportionality from a graph

This is an example of a graph with a line that is proportional. The constant of proportionality is 5. You can find the constant of proportionality by dividing one of the time values by the water values.

This is another example of a proportional relationship on a graph. The line goes through the origin (0, 0) and is a straight line. The constant of proportionality would be 50. In the context of the problem it takes 1 hour to get a total cost of $50.

This is an example of a non proportional relationship. In this situation, the line is a straight line, however the line does not cross the origin (0, 0).