The observations $7, 15, x-1, x+1, 24, 28$ have been arranged in ascending order. If the median of the data is $21$,find the value of $x$.

The mean of the data: $2, 8, 6, 5, 4, 5, 6, 3, 6, 4, 9, 1, 5, 6, 5$ is given to be $5$. Based on this information,is it correct to say that the mean of the data: $10, 12, 10, 2, 18, 8, 12, 6, 12, 10, 8, 10, 12, 16, 4$ is $10$? Give reason.

Let $m$ be the mid-point and $l$ be the upper class limit of a class in a continuous frequency distribution. The lower class limit of the class is:

The class marks of a continuous distribution are: $1.04, 1.14, 1.24, 1.34, 1.44, 1.54$ and $1.64$. Is it correct to say that the last interval will be $1.55-1.73$? Justify your answer.

If $\bar{x}$ is the mean of $x_{1}, x_{2}, \ldots, x_{n}$ and $\bar{y}$ is the mean of $y_{1}, y_{2}, \ldots, y_{n}$. If $\bar{z}$ is the mean of $x_{1}, x_{2}, \ldots, x_{n}, y_{1}, y_{2}, \ldots, y_{n}$,then $\bar{z}$ is equal to

Find the number of observations,if the sum of some observations is $975$ and their mean is $32.5$.