The formula for inverse variation is k equals x times y, where k is a constant quantity, x is one variable and y is another variable. Inverse variation is a concept from algebra and graphing in which an increase in one variable leads to a decrease in the second variable.
Although the formula to find the constant k is expressed as the product of x and y, the formula is usually expressed as y equals k divided by a, as this aids in the construction of graphs.
An example of inverse variation in the real world is speed versus time when traveling a fixed distance. A person who is traveling at high speed covers a distance in fewer units of time. In that particular example, the constant k is the distance, and speed and time are the variables x and y.