HMMT 十一月 2012 · 冲刺赛 · 第 8 题
HMMT November 2012 — Guts Round — Problem 8
题目详情
- [ 7 ] Three cards are drawn from the top of a shuffled standard 52-card deck. Find the probability that they are all of different suits. (A suit is either spades, clubs, hearts, or diamonds.)
解析
- [ 7 ] 169 Answer: There are 13 cards of each suit. The probability that the second card has a different 425 3 · 13 suit than the first is . The probability that the third card has a different suit than the first and 52 − 1 2 · 13 second card is 52 − 2 Since the two events need to both occur, we use the multiplicative rule: 3 · 13 2 · 13 · 52 − 1 52 − 2 169 = 425