Three coins were tossed $30$ times simultaneously. Each time the number of heads occurring was noted down as follows:
$\begin{array}{llllllllll}0 & 1 & 2 & 2 & 1 & 2 & 3 & 1 & 3 & 0 \\ 1 & 3 & 1 & 1 & 2 & 2 & 0 & 1 & 2 & 1 \\ 3 & 0 & 0 & 1 & 1 & 2 & 3 & 2 & 2 & 0\end{array}$
Prepare a frequency distribution table for the data given above.

Consider the marks,out of $100$,obtained by $51$ students of a class in a test,given in the table below. Draw a frequency polygon corresponding to this frequency distribution table.

Marks	Number of students
$0-10$	$5$
$10-20$	$10$
$20-30$	$4$
$30-40$	$6$
$40-50$	$7$
$50-60$	$3$
$60-70$	$2$
$70-80$	$2$
$80-90$	$3$
$90-100$	$9$
Total	$51$

$A$ study was conducted to find out the concentration of sulphur dioxide in the air in parts per million $(ppm)$ of a certain city. The data obtained for $30$ days is as follows:
$\begin{array}{llllll}0.03 & 0.08 & 0.08 & 0.09 & 0.04 & 0.17 \\ 0.16 & 0.05 & 0.02 & 0.06 & 0.18 & 0.20 \\ 0.11 & 0.08 & 0.12 & 0.13 & 0.22 & 0.07 \\ 0.08 & 0.01 & 0.10 & 0.06 & 0.09 & 0.18 \\ 0.11 & 0.07 & 0.05 & 0.07 & 0.01 & 0.04\end{array}$
$(i)$ Make a grouped frequency distribution table for this data with class intervals as $0.00 - 0.04, 0.04 - 0.08$,and so on.
$(ii)$ For how many days was the concentration of sulphur dioxide more than $0.11$ parts per million?

The following table gives the distribution of students of two sections according to the marks obtained by them:

Marks (Section $A$)	Frequency (Section $A$)	Marks (Section $B$)	Frequency (Section $B$)
$0-10$	$3$	$0-10$	$5$
$10-20$	$9$	$10-20$	$19$
$20-30$	$17$	$20-30$	$15$
$30-40$	$12$	$30-40$	$10$
$40-50$	$9$	$40-50$	$1$

Represent the marks of the students of both the sections on the same graph by two frequency polygons. From the two polygons,compare the performance of the two sections.

Find the mean salary of $60$ workers of a factory from the following table:

Salary (in Rs.)	Number of workers
$3000$	$16$
$4000$	$12$
$5000$	$10$
$6000$	$8$
$7000$	$6$
$8000$	$4$
$9000$	$3$
$10000$	$1$
Total	$60$

Give one example of a situation in which $(i)$ the mean is an appropriate measure of central tendency.