Trick with cards

Want to amaze your friends with magic tricks? Here is a trick with a deck of Cards.

Shuffle a deck of cards. Place the top card face up on the table and look at its number (Jack, Queen, King all equals 10). Put enough cards on top of the card to make the total 10. For example if a 7 were showing put 3 more cards on the top of it. Put the cards on so that all are face up. Keep making piles like this until deck is used up. If there are remaining cards that do not exactly equal to 10 hold onto them.
Ask someone in the audience to choose three piles, each with three or more cards in it, and flip them face down. Pick up rest of the piles. count 19 cards from those in your hand, and place them to the side, as they are necessary for rest of the trick.
Ask the volunteer to flip the top card of any of the three piles over, so that it is face up. From the cards in your hand, take the number of cards that corresponds to the number of the card flipped. For example if 2 is flipped, take 2 cards from your hand and keep it aside. Repeat this for another pile.
Count the number of cards in your hand, and tell the audience that this is the number of the top card in final(third) pile. Have the volunteer flip the card. The number always matches.