Q22:

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?

A. (m+4)/[m(m-4)]

B. (2m-4)/[m(m-4)]

C. (4m-4)/[m(m-4)]

D. (4m-8)/[m(m-4)]

E. (4m-12)/[m(m-4)]

这一题有些不懂，请指教。谢了。

就是说有四个三明治，我们设每个为a吧。有四个人很另类，偏偏不想吃第四块三明治，于是这第四块三明治就只能再剩下的m-4个人当中分了，那这m-4个人每人分到a/m-4块。剩下的三块三明治在m个人中分，每人分到3a/m块。既然c同学每个三明治都吃到了一点，那么他一定不属于另类的那四个人咯，so他吃到了（a/m-4）＋（3a/m）块三明治，再除以总数的4a就是答案e啦～

clear?

 再补充一下为什么不用除以4,

注意题目中的"what fraction of a whole extra-large sandwich" 问的是一

整块sandwich,不是全部4块.