有多少種方法可以從一副52張的撲克牌裏面抽出5張？

52張撲克牌共有 52 × 51 × 50 × 49 × ... × 3 × 2 × 1 = 52! 種排列。
將n設為未知數
n × (5張牌排列數) × (52-5)張牌排列數 = 52張撲克牌排列數
n × 5! × 47! = 52!
n × 5! = 52! / 47!
n × 5 × 4 × 3 × 2 × 1 = 52 × 51 × 50 × 49 × 48
n × 5 × 24 = 52 × 51 × 50 × 49 × 48
n = 52 × 51 × 50/5 × 49 × 48/24
n = 52 × 51 × 10 × 49 × 2
n = 2598960

2598960

52x51x50x49x48=311,875,200