2. 外语
  3. There are 5 cars, one yellow, one blue and three red. The cars are lined up in a row and cars of the same color have no differen

There are 5 cars, one yellow, one blue and three red. The cars are lined up in a row and cars of the same color have no differen

admin2021-10-21  30
问题 There are 5 cars, one yellow, one blue and three red. The cars are lined up in a row and cars of the same color have no difference. How many different arrangements are there?
选项 A、20
B、120
C、6
D、114
E、60
答案A
解析 题目意思是5辆车排成一排，1黄1蓝3红，一共有多少种不同的排列方法?
这道题目的关键是3辆红车之间没有任何区别，此题分两步走：
1.先从5个位置中选出2个来排1黄1蓝，共P52=20种排法。
2.剩下的3个位置刚好放置3辆红车，由于红车无区别，因此只有一种排法。于是题目所求得排列方法共有20种。
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