The $A.M.$ of a $50$ set of numbers is $38$. If two numbers of the set,namely $55$ and $45$,are discarded,the $A.M.$ of the remaining set of numbers is

If the mean of a data $\bar{x}$ is $10$ and if all the observations are multiplied by $2$,then the mean of the new data is

If the mean of $3, 4, x, 7, 10$ is $6$,then the value of $x$ is

Find the weighted mean of the first $n$ natural numbers,where the weights are equal to their squares.

Which of the following,in the case of discrete data,is not equal to the median?

$A$ school has four sections of chemistry in class $XII$ having $40, 35, 45$ and $42$ students. The mean marks obtained in chemistry test are $50, 60, 55$ and $45$ respectively for the four sections. The overall average of marks per student is: