If $\bar{x}$ represents the mean of $n$ observations $x_{1}, x_{2}, \ldots, x_{n},$ then the value of $\sum_{i=1}^{n}(x_{i}-\bar{x})$ is

The class mark of a frequency distribution with equal sizes of two successive classes is $72$ and $77$. Then,the width of the class is ...........

Draw a histogram for the data given below:

Class	$0-6$	$6-12$	$12-18$	$18-24$	$24-30$	$30-36$
Frequency	$7$	$10$	$12$	$15$	$10$	$6$

In a diagnostic test in mathematics given to students,the following marks (out of $100$) are recorded:
$46, 52, 48, 11, 41, 62, 54, 53, 96, 40, 98, 44$
Which 'average' will be a good representative of the above data and why?

Draw a frequency polygon for the following frequency distribution:

Class	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$	$70-80$
Frequency	$5$	$7$	$12$	$7$	$10$	$9$

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