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Eileenl · 发表于 2010-11-17 22:44:31

each of the integers from 0 to 9,inclusive,is written on a separate slip of blank paper and 10 slips are dropped into halt,if the slips are drawn one at a time whitn out replacement,how mang must drawn to ensure the number on two of the slips will have a sum of 10?
3 4 5 6 7?
daan7

sdcar2010 · 发表于 2010-11-17 23:12:44

7

How many must BE drawn to ensure the number on two of the slips will have a sum of 10?

You could end up with 6 numbers in hand, none of them could form a sum of 10: 0, 1, 2, 3, 4, 5.

Eileenl · 发表于 2010-11-18 16:48:28

终于找到了这道题的解法，要让两个数加起来正好为10，有（3,7）（4,6）（8,2）（1,9）四种可能，另外剩下了0,5，所以要保证有两个书架起来刚好为10，则要》6————————这个6是（）的个数以及剩下的书的个书0和5。

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所属分类: GMAT考试

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