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 no girl?
since, the team will not include any girl, therefore, only boys are to be selected. $5$ boys out of $7$ boys can be selected in $^{7} C _{5}$ ways.
Therefore, the required number of ways $=^{7} C _{5}=\frac{7 !}{5 ! 2 !}=\frac{6 \times 7}{2}=21$
The number of words from the letters of the word $'RAJASTHAN' $ by taking all the letters at a time in which vowels are alternate, are
The value of $r$ for which $^{20}{C_r}^{20}{C_0}{ + ^{20}}{C_{r - 1}}^{20}{C_1}{ + ^{20}}{C_{r - 2}}^{20}{C_2} + ...{ + ^{20}}{C_0}^{20}{C_r}$ is maximum is
If $^{{n^2} - n}{C_2}{ = ^{{n^2} - n}}{C_{10}}$, then $n = $
The number of four letter words that can be formed using the letters of the word $BARRACK$ is
$^{14}{C_4} + \sum\limits_{j = 1}^4 {^{18 - j}{C_3}} $ is equal to