A proportional column is two related quantities, one of which changes and the other changes accordingly. If the ratio (that is, quotient) of the corresponding two numbers in these two quantities is certain, then these two quantities are called the quantities in the proportional column, and the relationship between them is called the proportional column relationship.

, expressed by the formula: y/x = K. For example, the unit price of water is fixed, and the water fee is directly proportional to the water consumption.

Inverse ratio column refers to two related quantities, one of which is expanded or reduced by several times, and the other is reduced or expanded by the same multiple, but the product of the corresponding two numbers is certain. These two quantities are called inverse proportional quantities, and the relationship between them is called inverse proportional relationship. Use the formula: XY=K (certain). For example, the number of people is fixed, and the number of groups is inversely proportional to the number of people in each group.