general puzzles
| easy | general |
In a dark room, there is a deck of 52 cards, with exactly 10 cards facing up, rest are facing down. You can touch the cards with your hands but cannot sense which cards are facing up/down. You need to split all these cards into two decks with equal number of cards facing up!
We never said that both the final decks must have 5 cards each facing up.
Create a deck of 10 cards randomly from the original 52-card deck. And then turn over the 10-card deck.
This puzzle involves a trick, i.e, we can manually flip over any number of cards.
We create a deck of cards randomly selected from the deck.
Suppose the -card deck included number of cards that were originally facing up, and cards are facing up in the other deck.
By flipping over this -card deck, now there are exactly cards facing up in this deck, same as the other deck.
This question can be solved regardless of the original number , as long as we know the count of cards facing up.