If two quantities are related in such a way that if an increase in one quantity produces a proportional decrease in another quantity or if decrease in one quantity produces a proportional increase in another quantity, then the two quantities are known as inverse variations.

In inverse variation the quantity (variable) changes reversely when one of the quantities(variables) increases, the other one decreases.

In general, two quantities x and y are said to be in inverse proportion if an increase in x causes a proportional decrease in y and vice-versa, in such a manner that the product xy, of their corresponding values remains constant.