Q21. A body moves on a frictionless plane starting from rest. If $S _ { n }$ is distance moved between $t = n - 1$ and $\mathrm { t } = \mathrm { n }$ and $\mathrm { S } _ { \mathrm { n } - 1 }$ is distance moved between $\mathrm { t } = \mathrm { n } - 2$ and $\mathrm { t } = \mathrm { n } - 1$, then the ratio $\frac { \mathrm { S } _ { \mathrm { n } - 1 } } { \mathrm {~S} _ { \mathrm { n } } }$ is $\left( 1 - \frac { 2 } { x } \right)$ for $\mathrm { n } = 10$. The value of $x$ is $\_\_\_\_$ .
Q21. A body moves on a frictionless plane starting from rest. If $S _ { n }$ is distance moved between $t = n - 1$ and $\mathrm { t } = \mathrm { n }$ and $\mathrm { S } _ { \mathrm { n } - 1 }$ is distance moved between $\mathrm { t } = \mathrm { n } - 2$ and $\mathrm { t } = \mathrm { n } - 1$, then the ratio $\frac { \mathrm { S } _ { \mathrm { n } - 1 } } { \mathrm {~S} _ { \mathrm { n } } }$ is $\left( 1 - \frac { 2 } { x } \right)$ for $\mathrm { n } = 10$. The value of $x$ is $\_\_\_\_$ .