The average age of Ina,Mina,and Dika is $x$ years. After $y$ years,what will be their average age?

The marks obtained by $30$ students of Class $X$ of a certain school in a Mathematics paper consisting of $100$ marks are presented in the table below. Find the mean of the marks obtained by the students.

Marks obtained $(x_{i})$	$10, 20, 36, 40, 50, 56, 60, 70, 72, 80, 88, 92, 95$
Number of students $(f_{i})$	$1, 1, 3, 4, 3, 2, 4, 4, 1, 1, 2, 3, 1$

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

The mean of $15$ observations is $16$. If $2$ is added to each observation and then each result is divided by $3$,the new mean is:

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 $.675$)

Find the mean of the following frequency distribution:

Class	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$
Frequency	$2$	$10$	$40$	$25$	$13$	$10$

(in $.7$)