If $A=\{1,3,5,7,9,11,13,15,17\}, B=\{2,4, \ldots, 18\}$ and $N$ the set of natural numbers is the universal set, then $\left(A^{\prime} \cup(A \cup B) \cap B^{\prime}\right)$ is
If $S=\{x \mid x$ is a positive multiple of 3 less than 100 $\}$ and $P=\{x \mid x$ is a prime number less than 20$\}$. Then, $n(S)+n(P)$ is equal to
If $X$ and $Y$ are two sets and $X^{\prime}$ denotes the complement of $X$, then $X \cap(X \cup Y)^{\prime}$ is equal to
The set $\{x \in R: 1 \leq x<2\}$ can be written as ............. .
The set $\{x \in R: 1 \leq x<2\}$ can be written as $(1,2)$.
When $A=\phi$, then number of elements in $P(A)$ is .............. .
$$\begin{aligned} \therefore \quad & A =\phi \quad \Rightarrow n(A)=0 \\ & n\{P(A)\} =2^{n(A)}=2^0=1 \end{aligned} $$ So, number of element in $P(A)$ is 1 .