In a proportion with three terms, the mean term is the mean proportional between the two other terms.

The expression “mean proportional” is a synonym of “geometric mean“.

### Example

Consider this proportion:

\(\dfrac{2}{x}\) = \(\dfrac{x}{8}\)

The term \(x\) is a *mean proportional*.

We can calculate it with the geometric mean :

\(\overline{x}_g\) = \(\sqrt[2]{2 × 8}\) = \(\sqrt[2]{16} = 4\)