The arithmetic mean, the geometric mean, and the harmonic mean were studied by the Pythagorean society in about 500 BC. They are central to mathematics and have even more applications today than in ancient Greece! The three means can be represented geometrically, algebraically, and numerically.
Click HERE for an Overview of the Three Pythagorean Means (PDF)
These means are looked at in more detail in the Structure-Symmetry-Similarity progression.