JAMB 2013 · UTME · Q10

If $P = \{x : x \text{ is odd}, -1 < x \le 20\}$ and $Q = \{y : y \text{ is prime}, -2 < y \le 25\}$ , find $P \cap Q$ .

Worked solution (try it first)

$P$ is the odd numbers from 1 to 19: $\{1, 3, 5, \dots, 19\}$ .
$Q$ is the primes up to 25: $\{2, 3, 5, 7, 11, 13, 17, 19, 23\}$ .
The common elements are the odd primes up to 19: $\{3, 5, 7, 11, 13, 17, 19\}$ , option A.