Find the mean of the following frequency distribution:

$x_i$	$3$	$6$	$9$	$12$
$f_i$	$1$	$2$	$3$	$4$

For a symmetrical distribution,if ${Q_1} = 25$ and ${Q_3} = 45$,the median is

The median of a set of $13$ observations which are in decreasing order is $18.6$. If the first two observations are increased by $1$ and the last three observations are decreased by $5$,then the median of the set of new observations is-

Find the mean of the following frequency distribution:

$x_i$	$5$	$15$	$25$	$35$	$45$	$55$
$f_i$	$12$	$18$	$27$	$20$	$17$	$6$

If the mean of $n$ observations $1^2, 2^2, 3^2, \dots, n^2$ is $\frac{46n}{11}$,then what is the value of $n$?

Compute the median from the following table:

Marks obtained	No. of students
$0-10$	$2$
$10-20$	$18$
$20-30$	$30$
$30-40$	$45$
$40-50$	$35$
$50-60$	$20$
$60-70$	$6$
$70-80$	$3$