The probability of getting certain hands in blackjack is determined by the number of decks used and the specific rules of the game. For example, the probability of getting a blackjack in a single-deck game is about 4.8%, while the probability of getting a blackjack in an eight-deck game is about 4.7%. The probability of getting a pair in a single-deck game is about 12%, while the probability of getting a pair in an eight-deck game is about 11.6%.