Explanation

(b) From the theorem of parallel axis, the moment of inertia $I$ is equal to
$I = I_{CM} + Ma^{2}$
where $I_{CM}$ moment of inertia is about centre of mass and $a$ the distance of axis from centre.
$\therefore$ $I = MK^{2} + M \times (6)^{2}$
$MK_{1}^{2} = MK^{2} + 36M$
$\Rightarrow$ $K_{1}^{2} = K^{2} + 36$
$\Rightarrow$ $(10)^{2} = K^{2} + 36$
$\Rightarrow$ $K^{2} = 100 - 36 = 64$
$\Rightarrow$ $K = 8$ cm