Harmonic mean

The harmonic mean (frequently referred to as HM) is a special kind of mean (like Arithmetic mean, Geometric mean). The harmonic mean of n numbers $x_1, x_2... x_n$ is defined to be: $\frac{n} {\frac{1}{x_1}+\frac{1}{x_2}+...+\frac{1}{x_n}}$ . It is part of a large inequality, the Arithmetic mean-Harmonic mean-Geometric mean inequality, which states that AM>HM>GM.