If the mean of $4, 7, 2, 8, 6$ and $a$ is $7$,find the mean deviation about the median of these observations.

If the mean deviation about the mean of the numbers $1, 1 + d, 1 + 2d, \dots, 1 + 100d$ is $255$,then what is the value of $|d|$?

$\begin{aligned} &\text{Find the mean deviation about the mean for the following data:} \\ &\begin{array}{|l|c|c|c|c|c|} \hline \text{Class Interval} & 0-6 & 6-12 & 12-18 & 18-24 & 24-30 \\ \hline \text{Frequency} & 1 & 2 & 3 & 2 & 1 \\ \hline \end{array} \end{aligned}$

Calculate the mean deviation about the mean of the set of first $n$ natural numbers when $n$ is an odd number.

The mean deviation about the mean for the following data is:

$\text{Marks obtained}$	$0-10$	$10-20$	$20-30$	$30-40$	$40-50$
$\text{Number of Boys}$	$6$	$8$	$10$	$4$	$2$

What is the mean deviation of the numbers $1, 2, 3, 4, 5$?