A large number of particles are placed around the origin, each at a distance R from the origin. The  distance of the centre of mass of the system from the origin is 

As large number of particles are situated at a distance R from the origin. If particles are uniformly distributed and
make a circular boundary around the origin, then centre of mass will be at the origin.
While, if the particles are not uniformly distributed, then centre of mass will lie between particle and origin. This
implies that the distance between centre of mass and origin is always less than or equal to R.