The number of ways that $8$ beads of different colours can be strung as a necklace is

Which one of the following is mainly responsible for the depletion of the ozone layer?

If $0 < p < q$,then $\lim _{n \rightarrow \infty}\left(q^n+p^n\right)^{1 / n}$ is equal to :

If $a = i + j + k$,$a \cdot b = 1$ and $a \times b = j - k$,then $b = \dots$

An urn $A$ contains $3$ white and $5$ black balls. Another urn $B$ contains $6$ white and $8$ black balls. $A$ ball is picked from $A$ at random and then transferred to $B$. Then,a ball is picked at random from $B$. The probability that it is a white ball is

The area (in square units) of the region enclosed by the two circles $x^2+y^2=1$ and $(x-1)^2+y^2=1$ is