Which of the following arguments is valid?
Answer and explanation
Correct answer: C. If a number is divisible by 6 then it is even. The number 15 is not even. So 15 is not divisible by 6
- Step 1: The valid argument has the form , , therefore (modus tollens): not even, so not divisible by .
- Step 2: The others affirm the consequent or contradict the facts (8 is even but not divisible by 6; 9 is odd but not prime; 6 is even but not a multiple of 4).
Answer
If a number is divisible by 6 then it is even. The number 15 is not even. So 15 is not divisible by 6.
Why not the others: Each of the other arguments has true premises and a false conclusion, so none can be valid.
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