If $S_1$ and $S_2$ are the variances of the first $2k$ and $k$ $(k > 1)$ natural numbers respectively,then $(S_1 / S_2)$ lies in the interval

The mean and variance of a series of $5$ observations are $8$ and $24$ respectively. The mean and variance of another series of $3$ observations are $8$ and $24$ respectively. What is the variance of their combined series?

The variance of $\alpha$,$\beta$,and $\gamma$ is $9$. Then,the variance of $5\alpha$,$5\beta$,and $5\gamma$ is:

The variance of the following data is:

$x_i$	$6$	$10$	$14$	$18$	$24$	$28$	$30$
$f_i$	$2$	$4$	$7$	$12$	$8$	$4$	$3$

If $1$ is added to each of the first $10$ natural numbers,then the variance of the numbers so obtained is:

For $20$ observations of variable $x$,if $\sum(x_{i}-2)=20$ and $\sum(x_{i}-2)^2=100$,then the standard deviation of variable $x$ is