Find the mean of the first five prime numbers.

If $\bar{x}$ is the mean of $x_{1}, x_{2}, \ldots, x_{n},$ then for $a \neq 0,$ the mean of $a x_{1}, a x_{2}, \ldots, a x_{n}, \frac{x_{1}}{a}, \frac{x_{2}}{a}, \ldots, \frac{x_{n}}{a}$ is

The mean of $100$ observations is $50$. If one of the observations which was $50$ is replaced by $150$,the resulting mean will be:

The mean of the $10$ observations is $11$. If one new observation is included,their mean becomes $12$. The included new observation is ........

Draw a frequency polygon for the following frequency distribution:

Class	$0-10$	$10-20$	$20-30$	$30-40$	$40-50$
Frequency	$6$	$4$	$10$	$12$	$5$

Find the mean of the following frequency distribution:

Score $(x)$	$1$	$2$	$3$	$4$	$5$	$6$	$7$
Frequency $(f)$	$5$	$9$	$12$	$17$	$14$	$10$	$6$