Actually, Phil is right bud. If you have 55 cards out of two decks. And assume any of them can be chosen. Thats 55 cards, and you still can pick from those 55 cards, I.E. 55*55. Your way assumes all 112 cards are unique. There are doubles of each. So you need to divide your answer by 2. You should take a lesson from stats,
-ThrallMind