The cards in a deck show either a circle or a square on their faces and have backs that are either red or green. Four cards are dealt. Two are face down, showing red and green; two are face up, showing a circle and a square, thus:

[card 1] RED

[card 2] GREEN

[card 3] circle

[card 4] square

Someone asks: Of those four cards, does every RED one have a square on the other side? How many cards must be turned over to gain enough information to answer the question? Which ones?

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## bonanova 85

The cards in a deck show either a circle or a square on their faces and have backs that are either red or green. Four cards are dealt. Two are face down, showing red and green; two are face up, showing a circle and a square, thus:

[card 1] RED

[card 2] GREEN

[card 3] circle

[card 4] square

Someone asks: Of those four cards, does every RED one have a square on the other side? How many cards must be turned over to gain enough information to answer the question? Which ones?

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