WAEC 2020 · Paper 1 · Q14

Given that $P = \{x : 1 \le x \le 6\}$ and $Q = \{x : 2 < x < 10\}$ , where $x$ are integers, find $n(P \cap Q)$ .

Worked solution (try it first)

List the sets: $P = \{1, 2, 3, 4, 5, 6\}$ and $Q = \{3, 4, 5, 6, 7, 8, 9\}$ (2 and 10 are left out of $Q$ by the strict signs).
The elements in both are $P \cap Q = \{3, 4, 5, 6\}$ .
So $n(P \cap Q) = 4$ , option A.