Four identical thin rods each of mass M and length l form a square frame. Moment of inertia of this frame about an axis through the centre of the square and perpendicular to its plane is

The moment of inertia of each rod about an axis through the centre of frame but perpenducular to frame =[its moment of inertia through its centre of mass and perpendicular to rod + (mass of rod) ×(perpendicular distance between two axes)]= Ml212+M(l2)2 = Ml23Moment of inertia of the system = Ml23×4= 43Ml2