The moment of inertia of a cylinder about its own axis is equal to its moment of inertia about an axis passing through its centre and perpendicular to its length. The ratio of length to radius is

Let the moment of inertia of the cylinder about its own axis AB is I1, and moment of inertia about an axis passing through its centre and perpendicular to its length be I2.Then I1=I2or MR22=MR24+ML212 or R24=L212or L2R2=124=3  or  LR=31