The ratio of radius of gyration of a solid sphere of mass $M$ and radius $R$ about its own axis to the radius of gyration of the thin hollow sphere of same mass and radius about its axis is:

Radius of gyration of a solid sphere: $K_S=\sqrt{\frac{2}{5}}R$ Radius of gyration of a hollow sphere: $K_H=\sqrt{\frac{2}{3}}R$ $\Rightarrow \frac{K_S}{K_H}=\sqrt{\frac{3}{5}}=\frac{\sqrt{3}}{\sqrt{5}}$ Answer key in the source: (None).