WAEC 2022 · Paper 1 · Q15

Sets & logic

Given that $P = \{x : x \text{ is a multiple of } 5\}$ , $Q = \{x : x \text{ is a multiple of } 3\}$ and $R = \{x : x \text{ is an odd number}\}$ are subsets of $\mu = \{x : 20 \le x \le 35\}$ , find $(P \cup Q) \cap R$ .

Worked solution (try it first)

List the sets in $\mu$ : $P = \{20, 25, 30, 35\}$ and $Q = \{21, 24, 27, 30, 33\}$ .
The union holds everything in either: $P \cup Q = \{20, 21, 24, 25, 27, 30, 33, 35\}$ .
Keep only the odd numbers: $(P \cup Q) \cap R = \{21, 25, 27, 33, 35\}$ , option B.

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