Find the intersection of each pair of the following set : $A=\{x : x$ is a natural number and multiple of $3\},B=\{x : x$ is a natural number less than $6\}$

Question

$\begin{array}{1 1}(A)\;\{1,2,3,4,5,6\}&(B)\;\{3,6,9,12.....\}\\(C)\;\{3,6\}&(D)\;\{3\}\end{array} $

Answer 1

A={3,6,9,12.....}

B={1,2,3,4,5}

Here 3 is the common element to both A & B set

$\therefore A\cap B=\{3,6,9,12......\}\cap \{1,2,3,4,5\}$

$\Rightarrow \{3\}$

Hence (D) is the correct answer.