Find the arithmetic mean of the following frequency distribution.

$x_i$	$5$	$8$	$11$	$14$	$17$
$f_i$	$4$	$5$	$6$	$10$	$20$

Which formula is used to calculate the weighted mean?

The mean marks of $100$ students in a class in mathematics is $72$. If the number of boys is $70$ and their mean marks is $75$,find the mean marks of the girls in the class.

The mean weight per student in a group of seven students is $55 \ kg$. If the individual weights of $6$ students are $52, 58, 55, 53, 56$ and $54 \ kg$,then the weight of the seventh student is.....$kg$.

Which of the following averages is most affected by extreme observations?

If the mean of five observations $x, x + 2, x + 4, x + 6$,and $x + 8$ is $11$,what is the mean of the last three observations?