The mean of the first ten natural numbers is ........

For some given data, if $M = 15.4$ and $\bar{x} = 14.5$, then $Z = \dots$

The frequency distribution of marks obtained by $400$ students is given below. If the mean of the frequency distribution is $41.2$,find the missing frequencies $x$ and $y$.

Marks	$0-10$	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$	$70-80$
Number of students	$26$	$26$	$x$	$110$	$84$	$y$	$36$	$32$

Daily wages of $110$ workers,obtained in a survey,are tabulated below:

Daily wages (in $Rs.$)	Number of workers
$100-120$	$10$
$120-140$	$15$
$140-160$	$20$
$160-180$	$22$
$180-200$	$18$
$200-220$	$12$
$220-240$	$13$

Compute the mean daily wages of these workers (in $Rs.$).

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

Class	$20-25$	$25-30$	$30-35$	$35-40$	$40-45$	$45-50$	$50-55$
Frequency	$2$	$5$	$8$	$10$	$7$	$10$	$3$

In the formula $M = l + \frac{(\frac{n}{2} - cf)}{f} \times c$ for the median,$cf = \ldots \ldots \ldots$