A relationship between two equal ratios.
For example, the amount of flour and sugar in a recipe for cookies are a proportional relationship. Suzanne wants to bake four batches of cookies. Her recipe says that 1 cup of flour and 2 cups of sugar are needed to make 1 batch of cookies. In order to quadruple the recipe, Suzanne must multiply the quantity of every ingredient by four. After multiplying the original quantities by four, Suzanne is left with the proportion
The ratios of flour to sugar for the cookie receipe are in a proportional relationship with one another since they form equal ratios.