Two rods A and B of the same material and length have their radii r1 and r2 respectively. When they are rigidly fixed at one end and twisted by the same couple applied at the other end, the ratio of the angle of twist at the end of A and the angle of twist at the end of B is
τ=π nr421θ
In the given problem, r4θ= constant
Therefore θAθB=r42r41