What is the standard deviation of the numbers $31, 32, 33, \dots, 47$?

Find the variance of the sequence $a, a + d, a + 2d, \dots, a + 2nd$.

The outcome of each of $30$ items was observed; $10$ items gave an outcome $\frac{1}{2} - d$ each,$10$ items gave an outcome $\frac{1}{2}$ each,and the remaining $10$ items gave an outcome $\frac{1}{2} + d$ each. If the variance of this outcome data is $\frac{4}{3}$,then $|d|$ equals:

Let one angle of a triangle be $60^{\circ}$. If the variance of the three angles of the triangle is $4614^{\circ}$,then the other two angles are

If the sum of $10$ observations and the sum of their squares are $12$ and $18$ respectively,then the standard deviation of the observations is:

Let $x_1, x_2, \dots, x_{100}$ be $100$ observations such that $\sum x_i = 0$,$\sum_{1 \le i < j \le 100} |x_i x_j| = 80000$,and the mean deviation from their mean is $5$. Then their standard deviation is: