星际之门升天:概率问题
来源:百度文库 编辑:高校问答 时间:2024/05/12 15:43:06
it is required to place 7 white marble and 6 black marble in a row that the black marble occupies the even places. How many possible arrangements can be made?
a. 7!6!
b.3628800
c.Both a and b
d. None of them
a. 7!6!
b.3628800
c.Both a and b
d. None of them
c 但是还有可能是选d,因为marble黑白都是一样的,所以只有一种排法.
答案是C
题目意思是:7个白球和6个黑球摆成一排,黑球排在偶数位置(即第二,第四个位置放黑球),问有多少种排列方式?
答案是7!6!,也等于3628800
楼上速度好快啊!