Median and centroid of a triangle.

On the screen, we see a triangle ABC in black color. Line segments (red) are drawn from points A & B to the mid points of sides BC & AC respectively. These line segments in red color are called median and the point where these medians meet is called centroid. Move these points A, B and C and observe how the position of point G gets changed.
What relation do we see between the coordinates of A,B,C and G ?