## August 6, 2011

### Inverted Cards

A blind man was handed a deck of 52 cards with exactly 10 cards
facing up. How can he divide it into two piles, each of which
having the same number of cards facing up?

Anonymous said...

after putting 10cards, he can rotate upside down then he can have the cards facing up

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Mark said...

All he has to do is turn over any ten cards into a new pile. If a card is originally face down, then turning it over into a new pile adds a face up card to the new pile, but has no effect on the number of face down cards in the original pile. If the original card is face up, then turning it over into the new pile adds a face down card into the new pile, but diminishes the number of face up cards in the original pile by one. Doing this 10 times (the number of original face up cards) will result in the piles having equal numbers of face up cards.

chaitu said...

The 2 piles will be divided with 42 cards in one and 10 in the other. all the ten being removed are placed inverted to its previous state.