63. Two discs of same thickness but of different radii are made of two different materials such that their masses are same. The densities of the materials are in the ratio 1 : 3. The moments of inertia of these discs about the respective axes passing through their centres and perpendicular to their planes will be in the ratio
(a) 1 : 3
(b) 3 : 1
(c) 1 : 9
(d) 9 : 1
Ans. b
(44)