Find the constant of variation

Relationships that have straight-line graphs are called **linear relationships**.

The rate of change between any two points in a linear relationship is the same or *constant. *This constant ratio is called the **constant of variation**.

Rose can download two songs from the Internet each minute. This is shown in the table and in the graph.

Find the constant of variation.

Notice that as the number of songs increases by 2, the time in minutes increases by 1.

Constant of variation = songs per minute.