一道快晕死我的数学题...

ziwingfong

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

   ANSWER: 4m-12 / m(m-4)

  我是这么理解的：4块很大的三明治，m个学生分（m>4) ， 3个是m各学生平均分，1个是m-4个学生分 Carol 四个三明治 每个都吃一块 他吃的站总共三明治的多少

 难道是我理解错了 Carol 吃了4块啊 总共不就是 3m+(m-4）么 怎么出来的那个式子

 多谢执教

angelavivi

慢慢來看, 不难的.

Three of the sandwiches were evenly divided among the students
= 3cakes/m (每个student分到的量)

the fourth sandwich was evenly divided among the remaining students
= 1cake/(m-4) (剩下student分到的量)

 If Carol ate one piece from each of the four sandwiches
= Carol有吃了4块, 所以她吃到的量是 3cakes/m + 1cake/(m-4)

the amount of sandwich that she ate would be what fraction of a whole extra-large sandwich
= [3cakes/m + 1cake/(m-4)]/ (4cakes) --单位可消掉
= (4m-12)/ m(m-4)

longger

ding !!