
Moment of inertia of rod rotating about an axis passing through one end is I1=3ml2⋯(1)
Moment of inertia of ring rotating about one of its diameters is I2=2mR2.
Since the rod is bent into a ring, the circumference of the ring and the length of the rod are equal, l=2πR

Then, I2=2mR2=8π2ml2
Thus, the ratio I2I1=38π2, so x=8.