Find the mean of the distribution:

Class	$1-3$	$3-5$	$5-7$	$7-10$
Frequency	$9$	$22$	$27$	$17$

The following distribution gives the daily income of $50$ workers of a factory.

Daily income (in Rs.)	$100-120$	$120-140$	$140-160$	$160-180$	$180-200$
Number of workers	$12$	$14$	$8$	$6$	$10$

Convert the distribution above to a less than type cumulative frequency distribution,and draw its ogive.

Consider the following distribution:

Marks obtained	Number of students
More than or equal to $0$	$63$
More than or equal to $10$	$58$
More than or equal to $20$	$55$
More than or equal to $30$	$51$
More than or equal to $40$	$48$
More than or equal to $50$	$42$

The frequency of the class $30-40$ is:

Find the mean of the following frequency distribution:

Class	$21-25$	$26-30$	$31-35$	$36-40$	$41-45$	$46-50$	$51-55$
Frequency	$18$	$32$	$30$	$40$	$25$	$15$	$40$

(in $.675$)

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

For a given frequency distribution,$n=100, A=20$ and $\bar{x}=20$. Then,$\Sigma f_{i} d_{i}=\ldots \ldots \ldots . .$