The solution set of $^{10}{C_{x - 1}} > 2\;.{\;^{10}}{C_x}$ is
$ \left \{ 1,2,3, \right \}$
$\left \{4,5,6,\right \}$
$\left \{8,9,10,\right \}$
$\left \{ 9,10,11,\right \}$
$\sum \limits_{ k =0}^6{ }^{51- k } C _3$ is equal to
All possible two factors products are formed from numbers $1, 2, 3, 4, ...., 200$. The number of factors out of the total obtained which are multiples of $5$ is
All possible numbers are formed using the digits $1, 1, 2, 2, 2, 2, 3, 4, 4$ taken all at a time. The number of such numbers in which the odd digits occupy even places is
Let the number of elements in sets $A$ and $B$ be five and two respectively. Then the number of subsets of $A \times B$ each having at least $3$ and at most $6$ element is :
If $^{n + 1}{C_3} = 2{\,^n}{C_2},$ then $n =$