求解Prep的一道数学题！！

janelxf

In a class of 30 students, 2 didn't borrow any books from the library, 12students each borrowed 1 book, 10 students each borrowed 2 books and the rest of the students each borrowed at least 3 books. If the average number of books borrowed per student was 2, what is the maximum number of books that any single student could have borrowed?
答案是13，是怎么得出的呀？

eisowl

设另外6个人的平均借书为x本
(12＋20＋6x)/30=2
6x=28
也就是说这六个人平均借约4.8本，那有一个人最多的分配方式，就是其他人都借3本，设最多的人Y本
3×5＋y=28
y=13

zlin0222

30*2-12-10*2-(30-2-12-10-1)*3=13
假设剩下的人中只有一个人借的暴多，其他人都只借三本（下限）

janelxf

灰常感谢~~~