Card Trick - Declaring the Nth card

Split a deck of cards into two halves, say H1 and H2. Select any one half, say H2 and lay down all the cards face up one-by-one. Then pick them up without disturbing the original order and place them below H1.

Now, hold the deck so that the cards are facing down.
Draw the first card from the deck and place it face up. If it is any one of K,Q or J, consider it equivalent to a 10. The idea is as follows:

Let the card be 'x'. Now count from 'x' upto 10 and for each number in this count, draw a card from the deck and place it face down on 'x'.

Repeat the above procedure for two more cards, say 'y' and 'z'.
Now, let N = x + y + z.

Say that the Nth card in the remaining deck of cards in ur hand is so-and-so and then hey presto ! The Nth card is indeed what you said it would be.

Trick:
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Initially, when you are the putting down the cards from one of the halves, remember the 7th card.

Logic:
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Let the cards that are put down be x, y and z. Consider a card x. You draw cards from the deck and place them on x until you reach 10. That is, if the card is x, you draw (11-x) cards from the deck including x.

So initially, you draw (11-x + 11-y + 11-z) cards from the deck. Then, you draw N more cards from the deck where N = x + y + z.

Hence, in toto, you draw ( 11-x + 11-y + 11-z + x + y + z ) = 33 cards from the deck.

If you know the 33th card, you are done ! That is why, initially you lay down one of the halves and remember the 7th card and then place this half below the other.

So go ahead and take the second step in becoming a magician. The first one is ofcourse growing whiskers and acting strange and mysterious about anything and everything !!:D