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

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?

Calculate the mean,variance,and standard deviation for the following distribution.

Classes	$30-40$	$40-50$	$50-60$	$60-70$	$70-80$	$80-90$	$90-100$
Frequency $({f_i})$	$3$	$7$	$12$	$15$	$8$	$3$	$2$

The standard deviation of $a, a+d, a+2 d, \ldots, a+2 n d$ is

The mean of $100$ observations is $50$ and their standard deviation is $5$. Then,the sum of the squares of all the observations is:

Find the variance of the sequence $a, a + d, a + 2d, \dots, a + 2nd$.