Midpoint (Midvalue) of the class $15-30$ is ........

Calculate the mean of the scores of $20$ students in a mathematics test:

Marks	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$
Number of students	$2$	$4$	$7$	$6$	$1$

The formula to find the mean of an ungrouped data is ........

Calculate the mean of the frequency distribution of the marks scored by $100$ students in a mathematics test:

Marks	$0-10$	$10-20$	$20-30$	$30-40$	$40-50$
No. of students	$20$	$10$	$20$	$30$	$20$

The mean of ungrouped data and the mean calculated when the same data is grouped are always the same. Do you agree with this statement? Give reason for your answer.

In a frequency distribution with total frequency $48$,$\bar{x}=70$,$\Sigma f_{i}=43+f$,and $A=66$. Then,the missing frequency $f=$ .........