The mean of $25$ observations is $36$. If the mean of the first $13$ observations is $32$ and the mean of the last $13$ observations is $40$,find the $13^{\text{th}}$ observation.

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 ...........

....... is a branch of Mathematics in which the extraction of meaningful information is studied.

The information regarding the marks scored by $30$ students in a $50$ marks test is given below:

Marks $(x_{i})$	$15$	$22$	$28$	$31$	$35$	$40$	$44$	$46$
Number of students $(f_{i})$	$2$	$3$	$5$	$6$	$6$	$4$	$3$	$1$

Find the mean of the data.

$A$ grouped frequency table with class intervals of equal sizes using $250-270$ ($270$ not included in this interval) as one of the class intervals is constructed for the following data:
$268, 220, 368, 258, 242, 310, 272, 342$
$310, 290, 300, 320, 319, 304, 402, 318$
$406, 292, 354, 278, 210, 240, 330, 316$
$406, 215, 258, 236$
The frequency of the class $310-330$ is:

The mean of $10$ observations is $48$. If each observation is divided by $3$,what will be the new mean?