AoPS: The Four Cards

Shawn has dealt four cards in front of you. He claims that if a card has an even number on one side of it, then the other side of the card is blue. Which cards do you need to turn over, in order to confirm if Shawn is telling you the truth?

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AoPS, Art of Problem Solving, Education, Maths, Maths Challenge, Maths Problem Solving, Puzzle For The Day, School, Word ProblemsSarah NorrisLando EducationArt of Problem Solving, AoPS, Lando, Lando Education, cards, playing cards, maths, maths challenge, mathematics, maths puzzles, maths problem of the day, maths problems, mathematical puzzles, mathematical puzzle, telling the truthComment