Construction of a cumulative frequency table is useful in determining the

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 following frequency distribution is $60$ and the total frequency is $120$. Find the missing frequencies $f_{1}$ and $f_{2}$.

Class	$10-30$	$30-50$	$50-70$	$70-90$	$90-110$
Frequency	$17$	$f_{1}$	$32$	$f_{2}$	$19$

If the modal class of a frequency distribution is $70-85,$ then in the formula for mode,$l=$ ..........

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

For a given frequency distribution,$\Sigma f_{i} x_{i} = 1790$ and $\Sigma f_{i} = 50$. Then,the mean $\bar{x} = $ ..........