The mean deviation about the mean for the observations $ -1, 0, 4 $ is:

The frequency distribution of the age of students in a class of $40$ students is given below.

Age	$15$	$16$	$17$	$18$	$19$	$20$
No. of students	$5$	$8$	$5$	$12$	$X$	$Y$

If the mean deviation about the median is $1.25$,then $4X + 5Y$ is equal to:

The mean deviation from the mean of the series $(a), (a+d), (a+2d), \ldots, (a+2nd)$ is

Calculate the mean deviation about the median age for the age distribution of $100$ persons given below:

Age (in years)	$16-20$	$21-25$	$26-30$	$31-35$	$36-40$	$41-45$	$46-50$	$51-55$
Number of persons	$5$	$6$	$12$	$14$	$26$	$12$	$16$	$9$

For a frequency distribution,the mean deviation from the mean is computed by:

Find the mean deviation about the median of the following distribution:
$ \begin{array}{|l|l|l|l|l|l|} \hline \text{Marks obtained} & 10 & 11 & 12 & 14 & 15 \\ \hline \text{Number of students} & 2 & 3 & 8 & 3 & 4 \\ \hline \end{array} $