WAEC 2022 · Paper 1 · Q15

Logic

Consider the statements $p$ : Stephen is intelligent; $q$ : Stephen is good at Mathematics. If $p \Rightarrow q$ , which of the following is a valid conclusion?

Worked solution (try it first)

The implication $p$
$\Rightarrow q$ is equivalent to its contrapositive $\sim q$
$\Rightarrow \sim p$ : swap the parts and negate both.
$\sim q$ is "Stephen is not good at Mathematics" and $\sim p$ is "he is not intelligent".
So the valid conclusion is "If Stephen is not good at Mathematics, then he is not intelligent", option B.

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