The mean of $5$ observations is $16$. If an observation $5$ is replaced by $-5$,the new mean is ...........

Calculate the mean of the following data:

Class	$4-7$	$8-11$	$12-15$	$16-19$
Frequency	$5$	$4$	$9$	$10$

The mean of the following frequency distribution is $65$ and the total frequency is $100$. Find the missing frequencies $f_{1}$ and $f_{2}$.

Class	$15-35$	$35-55$	$55-75$	$75-95$	$95-115$
Frequency	$17$	$f_1$	$32$	$f_2$	$19$

For a given frequency distribution,$n=100$ and $\Sigma f_{i} x_{i}=245$. Then,$\bar{x}=\ldots \ldots \ldots \ldots$

Calculate the mean of the scores of $20$ students in a mathematics test:

Marks	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$
Number of students	$2$	$4$	$7$	$6$	$1$

$\sum_{i=1}^{10} (x_i - \bar{x}) = \dots$