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GATE 2017 CE (CE2) – Question 3

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

Four cards lie on a table, each with a number on one side and a colour on the other. Visible faces are 2, 3, red and blue. Proposition: If a card has an even value on one side, its opposite face is red. Which cards MUST be turned over to verify it?

  1. 2, red
  2. 2, 3, red
  3. 2, blue
  4. 2, red, blue

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Show answer and explanation

Correct answer: (C) 2, blue

Explanation

An implication fails only when its premise is true and its conclusion is false. Turn over 2 to check for red on its reverse, and blue to check that its reverse is not even. Neither 3 nor red can falsify the rule. Therefore C: 2 and blue.