GWD第一套题里面的数学题

qjy90

A photographerwill arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row.The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her.How many such arrangements of the 6 people are possible?

qjy90

哪位大侠指教下，谢谢啦！！

qjy90

就这样排我是排出来的哈，就想知道有没有比较简便的排列组合方法呢？？

tracy1991

把六个人从高到低标号为123456
第一排第一个必然是1
第二排最后一个必然是6
2只能放在1右边或者上面
即XX6   2Y6
 12Y   1XX
而Y的位置 第一种情况可以填345 所以有三种可能
         第二种情况可以填45   所以有两种可能
共5种

好像还是很麻烦~~希望你能看懂