Number of positive integral solution of the equation $xyz = 90$ is equal to :-
$60$
$108$
$54$
$120$
Out of $6$ boys and $4$ girls, a group of $7$ is to be formed. In how many ways can this be done if the group is to have a majority of boys
If $P(n,r) = 1680$ and $C(n,r) = 70$, then $69n + r! = $
The number of seven digit positive integers formed using the digits $1,2,3$ and $4$ only and sum of the digits equal to $12$ is $...........$.
On the occasion of Deepawali festival each student of a class sends greeting cards to the others. If there are $20$ students in the class, then the total number of greeting cards exchanged by the students is
If $n$ is even and the value of $^n{C_r}$ is maximum, then $r = $