After arranging the observations in ascending or descending order,the observation which is obtained in the middle is called .............. of the data.

The class mark of a frequency distribution with equal sizes of two successive classes is $72$ and $77$. Then,the width of the class is ...........

The class marks of a frequency distribution are given as follows: $15, 20, 25, \ldots$ The class interval corresponding to the class mark $20$ is:

If the mean of $18, 2x, 27, 12, 3x, 5x$ and $21$ is $24,$ then find $x$.

Draw a histogram for the following frequency distribution with unequal class length:

Class	$0-10$	$10-20$	$20-40$	$40-70$	$70-100$
Frequency	$15$	$13$	$28$	$36$	$27$

$30$ children were asked about the number of hours they watched $TV$ programmes last week. The results are recorded as under:

Number of hours	$0-5$	$5-10$	$10-15$	$15-20$
Frequency	$8$	$16$	$4$	$2$

Can we say that the number of children who watched $TV$ for $10$ or more hours a week is $22$? Justify your answer.