一个数学与英文相结合的题目In how many ways can you arrange the letters of the "think" so that the "t" and the "h" are separated by at least one other letter?麻烦说下解的方法
问题描述：
一个数学与英文相结合的题目
In how many ways can you arrange the letters of the "think" so that the "t" and the "h" are separated by at least one other letter?
麻烦说下解的方法
答
把t,h,i,n,k这五个字母拆开然后重新组合，问有几种方法能让t,h中间相隔至少一个其他字母。
解法嘛，不太了解。
答
30
答
72种吧
用排列组合
先排除了t和h那三个,用A33全排列等于6
然后3个字母产生了4个空位
t和k随便找两个就符合题意了
所以是A42等于12
根据乘法原理,就是6乘12
等于72种