Ratio is the quantification of a multiplicative relationship that is calculated by dividing (or multiplying) one quantity by another. Proportional problem involve situations in which the mathematical relationships are multiplicative in nature and allow the formation of two equal ratios between them. When solving ratio problems we use additive or multiplicative way of thinking. The first type is known as rate and illustrates a comparison between two variables with different units. "Pure ratios" are ratios that compare sizes of quantities with identical units or sizes of two quantities which are conceptually connected, but are not naturally considered as parts of a whole. Also proportion is considered to be direct or indirect linear relationship between two quantities and that means that corresponding elements of two sets are in proportion when there is a constant ratio. In keeping with the developmental process of the proportional scheme the individual is progressing from pre-formal strategies up to formal ones. A ratio between two quantities can be represented by a fraction, and thus the laws of fractions can be applied to ratios, as is explained below.