A blind man is handed a deck of 52 cards and told that exactly 10 of these cards are facing up. How can he divide the cards into two piles, not necessarily of equal size, with each pile having the same number of cards facing up?

Solution posted in comment 1.

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Solution in comments.

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- each row has exactly same number (4) of white and black squares.
- each column has exactly the same number (4) of white and black squares.

Show that the sum of numbers in the 32 white squared cells is equal to the sum of numbers in the 32 black squared cells.

UPDATE: Hint in comment 1.

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