M and R be the mass and radius of a disc. A small disc of radius R / 3 is removed from the bigger disc as shown in figure. The moment of inertia of…

$\displaystyle M$ and $\displaystyle R$ be the mass and radius of a disc. A small disc of radius $\displaystyle R / 3$ is removed from the bigger disc as shown in figure. The moment of inertia of remaining part of bigger disc about an axis AB passing through the centre O and perpendicular to the plane of disc is $\displaystyle \frac{4}{x} \mathrm{MR}^2$. The value of $\displaystyle x$ is $\displaystyle \_\_\_\_$.