In the formula $\bar{x} = \frac{\Sigma f_{i} x_{i}}{\Sigma f_{i}}$,$x_{i}$ represents ..........

For a given frequency distribution,$A=325, c=50, \Sigma f_{i} u_{i}=28$ and $\Sigma f_{i}=200$. Then,mean $\bar{x}=\ldots \ldots \ldots . .$

The mean of $15$ observations is $25$. Later on,it was found that one observation was taken by mistake as $20$ instead of $50$. Then,the correct mean is:

The class length of the excluding type of class $20-30$ in a frequency distribution is .......

$A$ class teacher has the following absentee record of $40$ students of a class for the whole term. Find the mean number of $days$ a student was absent.
$\begin{array}{|l|c|c|c|c|c|c|c|} \hline \text{Number of days} & 0-6 & 6-10 & 10-14 & 14-20 & 20-28 & 28-38 & 38-40 \\ \hline \text{Number of students} & 11 & 10 & 7 & 4 & 4 & 3 & 1 \\ \hline \end{array}$

In the formula $\bar{x} = \frac{\Sigma f_{i} x_{i}}{n}$,$f_{i}$ represents ..........