纠结一道题？

CrawlingY

Four extra-large sandwiches of exactly the same size were ordered for m students, where m > 4.  Three of the sandwiches were evenly divided among the students.  Since 4 students did not want any of the fourth sandwich, it was evenly divided among the remaining students.  If Carol ate one piece from each of the four sandwiches, the amount of sandwich that she ate would be what fraction of a whole extra-large sandwich?

myice

一共4个三明治。
前三个平均分配给了m个学生。
第四个平均分配给了(m-4)个学生。
如果每个三明治Carol都吃了，那么Carol吃掉的三明治总量占一个特大号三明治的多少？
假设一个特大号三明治的分量是X，那么
[3(X/m)+X/(m-4)]/X=[4m-12]/ [m(m-4)]

so 答案是：[4m-12]/ [m(m-4)]
希望帮到你

zhangyy85

还是版主厉害！