# Constant of Proportionality Review

## Definition

The constant of proportionality is the constant ratio found in a proportional relationship. The constant of proportionality and unit rate (which we learned about back in January) are actually the same thing. We always find the constant of proportionality by taking the y value and dividing it by the x value whether it's in a table or a graph.

## Proportional or not?

If you are looking at a table or graph, there has to be a constant for it to form a proportional relationship. You have to get the same number every time when you take y and divide it by x. If you don't get the same number, then it is not proportional.

We can also look at a graph and tell if it forms a proportional relationship. The graph of a proportional relationship has to form a straight line and it also has to go through the origin, which is the point (0,0) on a graph. The picture above shows a line that forms a proportional relationship.

## These are the same two videos as last time. Watch them again before moving on. The two videos are only 5 minutes total.

Finding Constant of Proportionality in a Table
8-R3-03: Determining proportionality and constant of proportion from a graph.