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Texas Instruments Logical Reasoning Logical Reasoning Medium

Analyze the given assumptions and the conclusion and choose the assumption X that makes the...

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Analyze the given assumptions and the conclusion and choose the assumption $X$ that makes the conclusion valid:

  • Assumption 1: All people travelling by a bike from city A to city B get mud on their sleeves.
  • Assumption 2: $X$
  • Conclusion: Keith travelled from city A to city B.

Which assumption $X$ logically guarantees the conclusion?

Choose one option.
Show answer & explanation
Answer: D. None of these

The given premise is a conditional statement (If Bike A->B, then Mud). To conclude that Keith traveled from A to B, we would need a premise stating that ONLY people traveling from A to B by bike get mud, and that Keith has mud. None of the options provide a sufficient condition to avoid the fallacy of affirming the consequent or to uniquely identify the route.

Step-by-step Derivation:
Step 1: Formalize Assumption 1. Let P be 'Travels by bike from A to B' and Q be 'Gets mud on sleeves'. Assumption 1 is: P → Q.
Step 2: Analyze the Conclusion. The conclusion is P ('Keith travelled from city A to city B').
Step 3: Evaluate Option A. 'Keith has mud on his sleeve (Q) and travelled by bike'. This gives us Q and the fact that he used a bike. However, P → Q does not imply Q → P. Having mud (Q) does not prove he traveled from A to B; he could have traveled from city C to city D and gotten mud there. Even knowing he used a bike, we don't know the route was A to B.
Step 4: Evaluate Option B. 'Keith travelled from city A'. This is only a partial component of P. It does not establish that he went to B or that he used a bike.
Step 5: Evaluate Option C. 'Keith travelled to city B'. Similarly, this is only a partial component of P.
Step 6: Conclusion. To make the conclusion P valid, we would need a statement like 'Only people traveling by bike from A to B get mud on their sleeves' AND 'Keith has mud on his sleeves'. Since none of the options provide a logically sufficient condition to derive P from the given premise, the correct answer is None of these.