Calculate the mean of the following data:

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

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 $Rs.$).

For a given frequency distribution,$A=49.5, \Sigma f_{i}=40, \Sigma f_{i} u_{i}=-5$ and $c=20$. Then,mean $\bar{x}=$ ............

If $x_{i}$ are the midpoints of the class intervals of grouped data,$f_{i}$ are the corresponding frequencies,and $\bar{x}$ is the mean,then $\sum (f_{i} x_{i} - f_{i} \bar{x})$ is equal to

For the calculation of mode of the following frequency distribution,$f_{0} = \dots \dots \dots \dots \dots$

Class	$1-3$	$3-5$	$5-7$	$7-9$	$9-11$
Frequency	$6$	$3$	$8$	$2$	$1$

Consider the data:

Class	$65-85$	$85-105$	$105-125$	$125-145$	$145-165$	$165-185$	$185-205$
Frequency	$4$	$5$	$13$	$20$	$14$	$7$	$4$

The difference between the upper limit of the median class and the lower limit of the modal class is: