The 6 playing cards may be arranged into 6 factorial (!) combinations, since the order of the cards does not matter, and since for each card we select, there is now one less card to choose from (for example 6 cards to start, then 5 to choose from, then 4, etc.) So the number of combinations is 6! = 6 x 5 x 4 x 3 x 2 x 1 = 720 combinations.