In the formula $\bar{x} = A + \frac{\Sigma f_{i} d_{i}}{\Sigma f_{i}}$,$d_{i} =$ .........

Find the median of the following frequency distribution:

Class	$0-5$	$5-10$	$10-15$	$15-20$	$20-25$	$25-30$	$30-35$
Frequency	$5$	$15$	$15$	$8$	$4$	$2$	$1$

Is it true to say that the mean,mode,and median of grouped data will always be different? Justify your answer.

In the formula $\bar{x} = a + h \left( \frac{\Sigma f_{i} u_{i}}{\Sigma f_{i}} \right)$,for finding the mean of grouped frequency distribution,$u_{i}$ is equal to

In the formula $\bar{x} = \frac{\Sigma f_{i} x_{i}}{\Sigma f_{i}}$,$x_{i}$ represents ..........

For a given frequency distribution,the frequencies of the first,second,and third class are $8$,$15$,and $18$ respectively. Then,the cumulative frequency of the third class is $\ldots \ldots \ldots \ldots .$