The GATE Grind

GATE 2023 CE (CE1) – Question 4

General Aptitude · Analytical Aptitude: Logical Reasoning and Deduction · 1 mark · Multiple choice

A duck named Donald Duck says "All ducks always lie."
Based only on the information above, which one of the following statements can be logically inferred with certainty?

  1. Donald Duck always lies.
  2. Donald Duck always tells the truth.
  3. Donald Duck's statement is true.
  4. Donald Duck's statement is false.

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Show answer and explanation

Correct answer: (D) Donald Duck's statement is false.

Explanation

If the statement were true, then all ducks lie, including Donald, so his statement would be a lie, which is a contradiction. So the statement is false. This only means that not all ducks always lie. It does not say whether Donald himself always lies.