1) Rate of change allows us to look at the relationship between variables and is expressed as a ratio of the dependent and independent variables. 2) The slope of a line represents its constant rate of change and is calculated by finding the change in the dependent variable over the change in the independent variable between two points. 3) The slope provides information about the relationship between the variables; for example, it can show the rate at which one variable changes in relation to the other, such as pages read per minute or cost per text message.