Proportional relationships can be expressed as equations or graphs. For example, the equation y = 2x describes a proportional relationship between two variables, where y is twice x. Similarly, a graph with a straight line that passes through the origin (0,0) indicates a proportional relationship between two variables.
Proportional relationships can also be expressed in terms of ratios. For instance, if y is twice x, then the ratio of y to x is 2:1.
Proportional relationships can also be expressed in terms of proportions. If y is twice x, then the proportion can be written as y/x = 2, or x/y = 1/2. This indicates that if x is twice as large as y, then y is half as large as x.