Find the mean deviation about the mean for the following data: $12, 3, 18, 17, 4, 9, 17, 19, 20, 15, 8, 17, 2, 3, 16, 11, 3, 1, 0, 5$.

The mean deviation from the mean of the data given below is

$\text{Marks}$	$10$	$15$	$20$	$25$	$30$
$\text{Number of students}$	$2$	$4$	$6$	$8$	$5$

What is the mean deviation about the mean for the observations $5, 10, 15, 20, \dots, 85$?

Let $O$ be the mean deviation of the first five odd natural numbers about their mean and $P$ be the mean deviation of the first five prime numbers about their mean. Then $P-O=$

If the mean deviation about the median of $x, 2x, 3x, 4x, 5x, 6x, 7x, 8x, 9x, 10x$ is $30$,then $|x|$ equals:

If the mean deviation about the mean of the numbers $1, 2, 3, \ldots, n$,where $n$ is odd,is $\frac{5(n+1)}{n}$,then $n$ is equal to