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1.Set Theory
medium
Sets $A$ and $B$ have $3$ and $6$ elements respectively. What can be the minimum number of elements in $A \cup B$
A
$3$
B
$6$
C
$9$
D
$18$
Solution
(b) $n(A \cup B) = n(A) + n(B) -n(A \cap B) $ = $3 + 6 – n(A \cap B)$
Since, maximum number of elements in $A \cap B = 3$
$\therefore $ Minimum number of elements in $A \cup B = 9 – 3 = 6$.
Standard 11
Mathematics