Find the mean of the following frequency distribution:

$x_i$	$5$	$15$	$25$	$35$	$45$	$55$
$f_i$	$12$	$18$	$27$	$20$	$17$	$6$

The geometric mean of the numbers $4, 5, 10, 20, 25$ is .........

If the mean of a set of observations $x_1, x_2, \dots, x_{10}$ is $20$,then find the mean of $x_1 + 4, x_2 + 8, x_3 + 12, \dots, x_{10} + 40$.

If for some $x \in R$,the frequency distribution of the marks obtained by $20$ students in a test is:
Marks: $2, 3, 5, 7$
Frequency: $(x+1)^2, 2x-5, x^2-3x, x$
Then the mean of the marks is:

The mean of the first three terms is $14$ and the mean of the next two terms is $18$. What is the mean of all five terms?

Find the mean of the following frequency distribution:

$x_i$	$3$	$6$	$9$	$12$
$f_i$	$1$	$2$	$3$	$4$