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

If the variance of the following frequency distribution is $50$,then $x$ is equal to:

Class	$10-20, 20-30, 30-40$
Frequency	$2, x, 2$

The mean of $5$ observations is $7$. If four of these observations are $6, 7, 8, 10$ and one is missing,then the variance of all the five observations is:

If $A$ and $B$ are the variances of the first $n$ even numbers and the first $n$ odd numbers respectively,then:

Find the standard deviation for the following data:

${x_i}$	$3$	$8$	$13$	$18$	$23$
${f_i}$	$7$	$10$	$15$	$10$	$6$

Suppose values taken by a variable $x$ are such that $a \le x_i \le b$,where $x_i$ denotes the value of $x$ in the $i^{th}$ case for $i = 1, 2, ..., n$. Then: