NECO 2023 · Paper 1 · Q10

Given sets $A = \{a, 1, c, 4, d\}$ , $B = \{b, 4, 0, 9, 7, 6\}$ and $C = \{a, 4, 8, 9, d, 2, 5\}$ , find $(A \cup B) \cap (A \cup C)$ .

Worked solution (try it first)

$A \cup B = \{a, 1, c, 4, d, b, 0, 9, 7, 6\}$ .
$A \cup C = \{a, 1, c, 4, d, 8, 9, 2, 5\}$ .
The elements in both are all of $A$ together with 9: $\{a, c, d, 1, 4, 9\}$ , option E.