For a given frequency distribution,$\bar{x}=54.3, \Sigma f_{i} u_{i}=2, n=25$ and $c=10$. Then the assumed mean $A = \dots$

For the following distribution,the modal class is:

Marks	Number of students
Below $10$	$3$
Below $20$	$12$
Below $30$	$27$
Below $40$	$57$
Below $50$	$75$
Below $60$	$80$

In the formula $Z = l + \left( \frac{f_{1} - f_{0}}{2f_{1} - f_{0} - f_{2}} \right) \times c$ for the mode,$f_{0} = \ldots \ldots \ldots$

The mean of the following data is $26.5$ and the total frequency is $60$. Find the missing frequencies $x$ and $y$.

Class	$0-10$	$10-20$	$20-30$	$30-40$	$40-50$
Frequency	$6$	$x$	$17$	$y$	$8$

In a maths test taken by $40$ students,the average score of $30$ boys is $16$ and the average score of $10$ girls is $12$. Which of the following gives the average score of the whole class?

The class length of the excluding type of class $20-30$ in a frequency distribution is .......