JAMB 2014 · UTME · Q10

If $P = \{1, 2, 3, 4, 5\}$ and $P \cup Q = \{1, 2, 3, 4, 5, 6, 7\}$ , list the elements in $Q$ .

Worked solution (try it first)

$P \cup Q$ holds every element of $P$ or $Q$ .
The elements 6 and 7 are in the union but not in $P$ , so both must come from $Q$ .
So $Q = \{6, 7\}$ , option D.