isi-entrance 2016 Q25

isi-entrance · India · UGA 4 marks Combinations & Selection Subset Counting with Set-Theoretic Conditions
Let $S = \{ 1, 2, \ldots, n \}$. The number of possible pairs of the form $(A, B)$ with $A \subseteq B$ for subsets $A$ and $B$ of $S$ is
(A) $2 ^ { n }$
(B) $3 ^ { n }$
(C) $\sum _ { k = 0 } ^ { n } \binom { n } { k } \binom { n } { n - k }$
(D) $n !$
Let $S = \{ 1, 2, \ldots, n \}$. The number of possible pairs of the form $(A, B)$ with $A \subseteq B$ for subsets $A$ and $B$ of $S$ is\\
(A) $2 ^ { n }$\\
(B) $3 ^ { n }$\\
(C) $\sum _ { k = 0 } ^ { n } \binom { n } { k } \binom { n } { n - k }$\\
(D) $n !$