What is the Term for the Center of Mass Equation Structure

Question

What is the term for the generic structure of this form of equation:

SUM(Mi * Xi) / SUM (Xi)

It is the same as the center of mass calculation.

Answer 1

It is a Weighted Mean.

http://en.wikipedia.org/wiki/Weighted_arithmetic_mean

Short, concise, but I must have this line. :)

Answer 2

Revised formula: SUM(Mi * Xi) / SUM (Mi)

The numerator is the (first) moment of mass about the origin. The denominator is the total mass.

The distribution of mass is modeled as a single mass having the same total mass as the distribution and located at the point (the center of mass) that produces the same moment of mass about the origin as the distribution.