The most stable measure of central tendency is

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

In a class of $100$ students,there are $70$ boys whose average marks in a subject are $75$. If the average marks of the complete class are $72$,then what are the average marks of the girls?

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?

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

The arithmetic mean of the first $n$ natural numbers is: