The range of the observations $2, 3, 5, 9, 8, 7, 6, 5, 7, 4, 3$ is . . . . . . .

The mean and variance of $7$ observations are $8$ and $16$ respectively. If two observations are $6$ and $8$,then the variance of the remaining $5$ observations is:

The mean monthly salary of the employees in a certain factory is Rs. $500$. The mean monthly salaries of male and female employees are respectively Rs. $510$ and Rs. $460$. The percentage of male employees in the factory is

The mean and variance of $7$ observations are $8$ and $16$ respectively. If one observation $14$ is omitted and $a$ and $b$ are respectively the mean and variance of the remaining $6$ observations,then $a+3b-5$ is equal to $..........$.

The average marks of boys in a class is $40$ and that of girls is $45$. The average marks of both boys and girls combined is $42$. Then the percentage of boys in the class is (in $\%$)

Based on the following statements,choose the correct option.
Statement-$I:$ The variance of the first $n$ even natural numbers is $\frac{n^2-1}{4}$.
Statement-$II:$ The difference between the variance of the first $20$ even natural numbers and their arithmetic mean is $112$.