For a given frequency distribution,$n=100, A=15$ and $\bar{x}=15$. Then,$\Sigma f_{i} d_{i} = \ldots$

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

The mean of the following frequency distribution is $52$. Find the missing frequency $f$.

Class	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$	$70-80$
Frequency	$5$	$3$	$4$	$f$	$2$	$6$	$13$

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	$2$	$4$	$7$	$6$	$1$

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	$20$	$10$	$20$	$30$	$20$

In the formula $\bar{x} = A + \frac{\Sigma f_{i} u_{i}}{\Sigma f_{i}} \times c$,$c$ represents .......