Let $m$ be the mid-point and $l$ be the upper class limit of a class in a continuous frequency distribution. The lower class limit of the class is:

If the marks obtained by the $20$ students are $6, 4, 9, 5, 9, 3, 7, 7, 5, 6, 9, 4, 10, 10, 4, 3, 6, 7, 9, 9$,then the mode of this data is .............

If the mean of $18, 2x, 27, 12, 3x, 5x$ and $21$ is $24,$ then find $x$.

If $\bar{x}_{1}, \bar{x}_{2}, \bar{x}_{3}, \ldots, \bar{x}_{n}$ are the means of $n$ groups with $n_{1}, n_{2}, \ldots, n_{n}$ number of observations respectively,then the combined mean $\bar{x}$ of all the groups taken together is given by:

State whether each of the following statements is true or false:
$(1)$ The median of the observations $12, 13, 14, 15, 16$ is $14$.
$(2)$ The mode of the observations $1, 3, 5, 7, 9$ is $5$.

Observations of a data are $28, 16, 9, 17, 82, 71, 41, 18, 25, 15$. Find the range of the data.