Question

Let A and B be two sets having 3 and 6 elements respectively. Write the minimum number of elements that $A\cup B$ can have.

Answer 1

If $A\subset B$ then $A\cup B$ = {$x:x\subset B$}

$n(A\cup B)$ = 6

If $A⊈B$ then $A\cup B$ = {$x:xϵAorxϵB$ }

$n(A\cup B)>6$