Mean of $50$ observations was found to be $80.4$. But later on,it was discovered that $96$ was misread as $69$ at one place. Find the correct mean.

The following table gives the distribution of students of sections $A$ and $B$ of a class according to the marks obtained by them.

Marks	Section $A$ Frequency	Section $B$ Frequency
$0-15$	$3$	$3$
$15-30$	$12$	$16$
$30-45$	$28$	$25$
$45-60$	$30$	$27$
$60-75$	$35$	$40$
$75-90$	$13$	$10$

Represent the marks of the students of both the sections on the same graph by two frequency polygons. What do you observe?

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

Three coins were tossed $30$ times simultaneously. Each time the number of heads occurring was noted down as follows:
$0, 1, 2, 2, 1, 2, 3, 1, 3, 0,$
$1, 3, 1, 1, 2, 2, 0, 1, 2, 1,$
$3, 0, 0, 1, 1, 2, 3, 2, 2, 0$
Prepare a frequency distribution table for the data given above.

$A$ die is thrown $1000$ times and the outcomes were recorded as follows:

Outcome	$1$	$2$	$3$	$4$	$5$	$6$
Frequency	$180$	$150$	$160$	$170$	$150$	$190$

If the die is thrown once more,then the probability that it shows $5$ is:

For drawing a frequency polygon of a continuous frequency distribution,we plot the points whose ordinates are the frequencies of the respective classes and abscissae are respectively: