The distance between the origin and the centroid of the tetrahedron whose vertices are (0,0,0), (a,0,0), (0,b,0), (0,0,c) is
a2+b2+c2
a2+b2+c22
a2+b2+c24
4a2+b2+c2
Centroid of the tetrahedron G=a4,b4,c4.
∴OG=a2+b2+c24