A circular disc reaches from top to bottom of an inclined plane of length $L$. When it slips down the plane, it takes time $t _ { 1 }$. When it rolls down the plane, it takes time $t _ { 2 }$. The value of $\frac { t _ { 2 } } { t _ { 1 } }$ is $\sqrt { \frac { 3 } { x } }$. The value of $x$ will be