Pack of cards

[minniemoo]

How many times would you need to shuffle a pack of cards to end up with the pack in the same order as when you started.

[kempie]

The answer lies somewhere between 1 and infinity.

[geo0939]

Lots and lots.

[sire]

None

[kempie]

That's bad grammar.

It is impossible to shuffle a pack zero times.

[Fibonacci]

From wikipedia
Shuffling techniques
Faro Shuffle
The Faro Shuffle is performed by cutting the deck into two, preferably equal, packs in both hands as follows (right-handed): The cards are held from above in the right and from below in the left hand. Separation of the deck is done simply lifting up half the cards with the right hand thumb slightly and pushing the left hand's packet forward away from the right hand. The two packets are often crossed and slammed into each other as to align them. They are then pushed together by the short sides and bent (either up or down). The cards will then alternately fall into each other, much like a zipper. A flourish can by added by springing the packets together by applying pressure and bending them from above.

A perfect Faro Shuffle, where the cards are perfectly alternated, is considered on of the most difficult sleights by card magicians, simply because it requires the shuffler to be able to cut the deck into two equal packets and apply just about the right pressure when pushing the cards into each other. If one does perform 8 perfect Faro Shuffles in a row, the order of the deck will return to the original order, if there are 52 cards in the deck.

[minniemoo]

Fibonnaci thank you - this was actually a question my husband asked me to post and he was convinced that there could not be a possible answer. He was so impressed by your answer (as I was) that he has now registered with this site.