$\mathop \sum \limits_{0 \le i < j \le n} i\left( \begin{array}{l}
n\\
j
\end{array} \right)$ is equal to
$n^22^{n-1}$
$(n^2 -1)2^{n-1}$
$(n-1)^22^n$
$n(n-1)2^{n-3}$
A class contains $b$ boys and $g$ girls. If the number of ways of selecting $3$ boys and $2$ girls from the class is $168$, then $b +3\,g$ is equal to.
How many words can be made from the letters of the word $BHARAT$ in which $ B $ and $H$ never come together
In how many ways can $5$ red and $4$ white balls be drawn from a bag containing $10$ red and $8$ white balls
There were two women participating in a chess tournament. Every participant played two games with the other participants. The number of games that the men played between themselves proved to exceed by $66$ the number of games that the men played with the women. The number of participants is
The number of matrices of order $3 \times 3$, whose entries are either $0$ or $1$ and the sum of all the entries is a prime number, is$....$