The number of ways, $16$ identical cubes, of which $11$ are blue and rest are red, can be placed in a row so that between any two red cubes there should be at least $2$ blue cubes, is
$56$
$66$
$76$
$86$
The set $S = \left\{ {1,2,3, \ldots ,12} \right\}$ is to be partitioned into three sets $A,\,B,\, C$ of equal size . Thus $A \cup B \cup C = S$ અને $A \cap B = B \cap C = C \cap A = \emptyset $ . The number of ways to partition $S$ is
$^n{C_r}{ + ^n}{C_{r - 1}}$ is equal to
In how many ways can $6$ persons be selected from $4$ officers and $8$ constables, if at least one officer is to be included
If $^n{C_3} + {\,^n}{C_4} > {\,^{n + 1}}{C_3},$ then
A set contains $2n + 1$ elements. The number of subsets of this set containing more than $n$ elements is equal to