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标题: 求教一道prep数学题 [打印本页]

作者: mishasage 时间: 2009-10-15 16:16
标题: 求教一道prep数学题
in a class of 30 students, 2 students did not borrow any books from library. 12 students each borrowed 1 book, 10 each borrowed 2 books, and the rest of the students borrowed at least 3 books, if the average number of books borrowed per student was 2, what's the maximum number of books that a single student could have borrow?

A.3
B.5
C.8
D.13
E.15

完全没思路啊````

作者: biglin1987 时间: 2009-10-15 16:28

30个学生，平均每人2本，可以得出书总数2*30=60

60本里减去12本（12 students each borrowed 1 book），再减去20本（10 each borrowed 2 books），得60-1*12-2*10=28。

这28是剩下6个人的（30-2-12-10=6），每人至少3本，那么让其中5个人每人拿3本，剩下那个人就是拿得最多的，即28本-3本/人*5人=13本

故选d

作者: mishasage 时间: 2009-10-15 17:19
十分感谢！想想其实也不难的

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