$Z - M = \ldots \ldots \ldots \times (M - \bar{x})$

Find the mean of the following data:

Class	$200-299$	$300-399$	$400-499$	$500-599$	$600-699$	$700-799$	$800-899$
Frequency	$3$	$61$	$118$	$139$	$126$	$151$	$2$

Cumulative frequency curve is also known as ........

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 mean of the following frequency distribution is $60$ and the total frequency is $120$. Find the missing frequencies $f_{1}$ and $f_{2}$.

Class	$10-30$	$30-50$	$50-70$	$70-90$	$90-110$
Frequency	$17$	$f_{1}$	$32$	$f_{2}$	$19$

Construct the cumulative frequency distribution of the following distribution:

Class	$12.5-17.5$	$17.5-22.5$	$22.5-27.5$	$27.5-32.5$	$32.5-37.5$
Frequency	$2$	$22$	$19$	$14$	$13$