WAEC 2022 Mathematics · Question 16
Consider the statements: p: Stephen is intelligent q: Stephen is good at Mathematics If p⇒q, which of the following is a valid conclusion?
Options
- A.If Stephen is good at Mathematics, then he is intelligent
- B.If Stephen is not good at Mathematics, then he is not intelligent
- C.If Stephen is not intelligent, then he is not good at Mathematics
- D.If Stephen is not good at Mathematics, then he is intelligent
Answer: B. If Stephen is not good at Mathematics, then he is not intelligent
Explanation written with AI and checked against the answer key
Analyze the question
We are given the conditional statement p ⇒ q, meaning "If Stephen is intelligent, then he is good at Mathematics." We need to find which statement must logically follow from it.
Concept: Related conditional statements
For p ⇒ q:
- Converse: q ⇒ p (not necessarily valid)
- Inverse: ~p ⇒ ~q (not necessarily valid)
- Contrapositive: ~q ⇒ ~p (always logically equivalent to the original, so it is valid)
Check each option
- A. "If Stephen is good at Mathematics, then he is intelligent" is q ⇒ p. This is the converse, so it is not valid.
- B. "If Stephen is not good at Mathematics, then he is not intelligent" is ~q ⇒ ~p. This is the contrapositive, so it is valid.
- C. "If Stephen is not intelligent, then he is not good at Mathematics" is ~p ⇒ ~q. This is the inverse, so it is not valid.
- D. "If Stephen is not good at Mathematics, then he is intelligent" is ~q ⇒ p. This does not follow from p ⇒ q.
Answer
The contrapositive, option B, is the only valid conclusion.
Tip: To find the contrapositive, swap the two statements and negate both: p ⇒ q becomes ~q ⇒ ~p. Remember, "flip and negate." The converse and inverse are traps that WASSCE, NECO, and JAMB love to include as wrong options.
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