The variance of $20$ observations is $5$. If each observation is multiplied by $2$,then the variance of the resulting observations is:

Which insecticide is used for termite control in buildings?

$\int_0^{\pi / 2} \frac{d x}{1+\tan ^3 x}$ is equal to :

If $\frac{x-4}{x^2-5x-2k} = \frac{2}{x-2} - \frac{1}{x+k}$,then $k$ is equal to

The secretion from the abdominal glands of honey bees is ..........

The area of the triangle $ABC$ is $10 \sqrt{3} \text{ cm}^2$,angle $B$ is $60^{\circ}$ and its perimeter is $20 \text{ cm}$,then $\ell(AC) = $ (in $\text{ cm}$)