The number of ordered pairs ( $\mathrm{r}, \mathrm{k}$ ) for which $6 \cdot ^{35} \mathrm{C}_{\mathrm{r}}=\left(\mathrm{k}^{2}-3\right)\cdot{^{36} \mathrm{C}_{\mathrm{r}+1}}$. where $\mathrm{k}$ is an integer, is
$3$
$2$
$4$
$6$
A group consists of $4$ girls and $7$ boys. In how many ways can a team of $5$ members be selected if the team has at least $3$ girls $?$
$^n{P_r}{ \div ^n}{C_r}$ =
${ }^{n-1} C_r=\left(k^2-8\right){ }^n C_{r+1}$ if and only if:
The numbers of permutations of $n$ things taken $r$ at a time, when $p$ things are always included, is
The total number of ways of selecting six coins out of $20$ one rupee coins, $10$ fifty paise coins and $7$ twenty five paise coins is