Moment of inertia of a disc of mass $M$ and radius ' $R$ ' about any of its diameter is $\frac { M R ^ { 2 } } { 4 }$. The moment of inertia of this disc about an axis normal to the disc and passing through a point on its edge will be, $\frac { x } { 2 } M R ^ { 2 }$. The value of $x$ is $\_\_\_\_$ .