Calculate the mean of the following data:

Class	$4-7$	$8-11$	$12-15$	$16-19$
Frequency	$5$	$4$	$9$	$10$

The median class of the following frequency distribution is ...........

Class	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$	$70-80$
Frequency	$6$	$10$	$5$	$6$	$4$	$2$	$2$

The times,in seconds,taken by $150$ athletes to run a $110\, m$ hurdle race are tabulated below:

Class (seconds)	$13.8-14.0$	$14.0-14.2$	$14.2-14.4$	$14.4-14.6$	$14.6-14.8$	$14.8-15.0$
Frequency	$2$	$4$	$5$	$71$	$48$	$20$

The number of athletes who completed the race in less than $14.6\, s$ is:

The daily income of a sample of $50$ employees is tabulated as follows:

Income (in $Rs.$)	$1-200$	$201-400$	$401-600$	$601-800$
Number of employees	$14$	$15$	$14$	$7$

Find the mean daily income of the employees. (in $.5$)

For the following distribution,the modal class is:

Marks	Number of students
Below $10$	$3$
Below $20$	$12$
Below $30$	$27$
Below $40$	$57$
Below $50$	$75$
Below $60$	$80$

For some given data,if $M + \bar{x} = 32$ and $M - \bar{x} = 2$,then $Z = \ldots \ldots \ldots$