Question

Given A = {$x$ : $xϵN$ and $3<x\le 6$} and B = {$x$ : $xϵW$ and $x<4$}. Find the number of elements in A $\cap$ B.

Answer 1

$A=\{x:x\in N,3<x\le 6\}$
$\therefore A=\{4,5,6\}$
$B=\{x:x\in W,x<4\}$
$\therefore B=\{0,1,2,3\}$ [$x\in W$ i.e., whole number]
$A\cap B=$ Contains elements common to sets $A$ and $B$
$\therefore A\cap B=\varphi$,where $\varphi$ is empty set

Hence, 0 will be correct answer.