If the mean deviation of the numbers $1, 1+d, 1+2d, \dots, 1+100d$ from their mean is $255$,then $d$ is equal to:

In a series of $3n$ observations,if $n$ observations are equal to $a$ and the remaining $2n$ observations are equal to $-2a$,then the mean deviation of the observations about their mean is:

The following data represents the frequency distribution of $20$ observations.

$x_i$	$3$	$4$	$5$	$8$	$10$	$11$
$f_i$	$\alpha+2$	$(\alpha-1)^2$	$4$	$\alpha-1$	$2$	$\alpha$

Then its mean deviation about the mean is

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

Find the mean deviation about the mean for the given data:

$x_i$	$5$	$10$	$15$	$20$	$25$
$f_i$	$7$	$4$	$6$	$3$	$5$

Find the mean deviation about the mean for the following data:

${x_i}$	$2$	$5$	$6$	$8$	$10$	$12$
${f_i}$	$2$	$8$	$10$	$7$	$8$	$5$