For some given data,if $M = 62.5$ and $\bar{x} = 64$,then $Z = \ldots$

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 $.5$)

Find the mean,median and mode of the following frequency distribution:

Class	$0-30$	$30-60$	$60-90$	$90-120$	$120-150$	$150-180$
Frequency	$8$	$15$	$16$	$20$	$12$	$9$

The following table gives the number of pages written by Sarika for completing her own book over $30$ days:

Number of pages written per day	$16-18$	$19-21$	$22-24$	$25-27$	$28-30$
Number of days	$1$	$3$	$4$	$9$	$13$

Find the mean number of pages written per day.

The following is the cumulative frequency distribution (of less than type) of $1000$ persons each of age $20$ $years$ and above. Determine the mean age.

Age (years)	$30$	$40$	$50$	$60$	$70$	$80$
Cumulative Frequency	$100$	$220$	$350$	$750$	$950$	$1000$

For a given frequency distribution,the cumulative frequency of the fourth class is $25$ and the frequency of the fourth class is $10$. Then,the cumulative frequency of the third class is ...............