As shown in the figure,two thin coplanar circular discs $A$ and $B$ each of mass $M$ and radius $r$ are attached to form a rigid body. The moment of inertia of this system about an axis perpendicular to the plane of disc $B$ and passing through its centre is (in $Mr^2$)

From a circular disc of radius $R$ and mass $9M$,a small disc of radius $\frac{R}{3}$ is removed concentrically. If the mass of the removed disc is $M$,what is the moment of inertia of the remaining disc about an axis perpendicular to the plane of the disc and passing through its centre?

$A$ solid sphere of mass $M$ and a disc of mass $M/2$ have the same radius $R$. The ratio of the moment of inertia of the disc about a tangent in its plane to the moment of inertia of the sphere about its tangent is:

From a disc of mass $M$ and radius $R$,a circular hole of diameter $R$ is cut whose rim passes through the centre. The moment of inertia of the remaining part of the disc about a perpendicular axis passing through the centre is

$A$ thin rod has a length of $1 \ m$ and a mass of $0.6 \ kg$. The moment of inertia of the rod about an axis perpendicular to its length and passing through a point $20 \ cm$ from one end is ................... $kg \cdot m^2$ (the width of the rod is negligible).

The moment of inertia of a uniform ring of mass $M$ and radius $r$ about a tangent in its own plane is: