A solid sphere of mass M and radius R is divided into two unequal parts. The smaller part having mass M / 8 is converted into a sphere of radius r…

A solid sphere of mass $\displaystyle M$ and radius $\displaystyle R$ is divided into two unequal parts. The smaller part having mass $\displaystyle M / 8$ is converted into a sphere of radius $\displaystyle r$ and the larger part is converted into a circular disc of thickness $\displaystyle t$ and radius $\displaystyle 2 R$. If $\displaystyle I_1$ is moment of inertia of a sphere having radius $\displaystyle r$ about an axis through its centre and $\displaystyle I_2$ is the moment of inertia of a disc about its diameter, the ratio of their moment of inertia $\displaystyle I_2 / I_1=$ $\displaystyle \_\_\_\_$.