The median of the following observations arranged in ascending order is $53 :$ $41, 48, x+1, x+5, 62, 72$. Find $x$.

The mean of $3, -3, -3, 3, 3, -3$ is ..........

The class mark of the class $90-120$ is:

The blood groups of $30$ students are recorded as follows:
$A, B, O, A, AB, O, A, O, B, A, O, B, A, AB, B, A, AB, B$
$A, A, O, A, AB, B, A, O, B, A, B, A$
Prepare a frequency distribution table for the data.

Below is the distribution of "more than" type of marks obtained by $50$ students in a $100$ marks examination. Prepare the grouped frequency distribution from that.

Obtained marks	No. of Students
$0$ or more than $0$	$50$
$20$ or more than $20$	$48$
$40$ or more than $40$	$40$
$60$ or more than $60$	$31$
$80$ or more than $80$	$10$

If $\bar{x}_{1}, \bar{x}_{2}, \bar{x}_{3}, \ldots, \bar{x}_{n}$ are the means of $n$ groups with $n_{1}, n_{2}, \ldots, n_{n}$ number of observations respectively,then the combined mean $\bar{x}$ of all the groups taken together is given by: