If the coefficient of variation and standard deviation are $ 60 $ and $ 21 $ respectively,the arithmetic mean of the distribution is:

If the mean of the data $7, 8, 9, 7, 8, 7, \lambda, 8$ is $8$,then the variance of the data is:

Find the variance of the following discrete frequency distribution:

Class Interval	$0-2$	$2-4$	$4-6$	$6-8$	$8-10$
Frequency $(f_i)$	$2$	$3$	$5$	$3$	$2$

Variance of first $2n$ natural numbers is

The marks obtained by students $A$ and $B$ in $3$ examinations are given below:
| | Exam $1$ | Exam $2$ | Exam $3$ |
|---|---|---|---|
| Marks of $A$ | $30$ | $20$ | $40$ |
| Marks of $B$ | $70$ | $0$ | $5$ |
The ratio of the coefficient of variation of marks of $A$ and the coefficient of variation of marks of $B$ is:

The variance of the discrete data $3, 4, 5, 6, 7, 8, 10, 13$ is