The general formula for inverse variation is k equals y times x, where k is a constant quantity, y is one variable and x is another variable. Under inverse variation, when one variable increases, the other decreases.
This is more easily seen when the formula is rewritten to solve for y, as is often the case when plotting points on a graph. In that case, the formula is expressed as y equals k divided by x. Since k always remains the same, as x increases, the result of that division must decrease. A simple example of inverse variation in the real world is slice size versus number of slices when dividing up a cake. Since the cake is a constant size, as the size of each slice increases, the number of individual slices must decrease.