$A$ student obtains $75\%$,$80\%$,and $85\%$ in three subjects. If the marks of a fourth subject are added,then his average cannot be less than.....$\%$

The following data gives the distribution of height of students:

Height (in $cm$)	$160$	$150$	$152$	$161$	$156$	$154$	$155$
No of students	$12$	$8$	$4$	$4$	$3$	$3$	$7$

The median of the distribution is:

In a data,if the number $i$ is repeated $i$ times for $i=1, 2, \ldots, n$,then the mean of the data is

If a variable takes the discrete values $\alpha - 4, \alpha - \frac{7}{2}, \alpha - \frac{5}{2}, \alpha - 3, \alpha - 2, \alpha + \frac{1}{2}, \alpha - \frac{1}{2}, \alpha + 5$ (where $\alpha > 0$),then the median is:

The average of $n$ numbers $x_1, x_2, x_3, ..., x_n$ is $M$. If $x_n$ is replaced by $x'$,then the new average is:

If the mean of the set of numbers ${x_1}, {x_2}, {x_3}, ..., {x_n}$ is $\bar x$,then the mean of the numbers ${x_i} + 2i$,$1 \le i \le n$ is