Question

Let $X=\left\{n\,\epsilon\,N : 1\,\le\,n\,\le\,50\right\}$. If
$A =$ { $n\,\epsilon \,X$ : n is a multiple of 2} and
$B =$ { $n\, \epsilon\, X$ : n is a multiple of 7}, then the number of elements in the smallest subset of X containing both A and B is__________.
Given 7

Answer 1

$n\left(A\right) =25
n\left(B\right) = 7$
$n\left(A\cap B\right)=3$
$n\left(A\cup B\right)=25+7-3=29$