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标题: one JJ math question... [打印本页]

作者: redhat 时间: 2002-10-29 22:33 标题: one JJ math question...

34 . Each of the integers from 0 to 9, inclusive, is written on a separate slip of blank paper and the ten slips are dropped into a hat. If the slips are then drawn one at a time without replacement, how many must be drawn to ensure that the numbers on two of the slips drawn will have a sun of 10?

ANS.
E) 7

Could anybody figure out how to solve this question??[em14]
Thanx a lot![em09]

作者: 猫猫头 时间: 2002-10-29 22:44

0，1，2，3，4，5，6
got it?

作者: redhat 时间: 2002-10-29 22:56

I was confused by the explanation:

0到9的整数有4种可能相加为10,即1+9, 2+8, 3+7, 4+6，剩下0和5不可能与另一张纸条相加为10，要想保证抽出的2张纸条上的数字相加为10则必须抽7次

...anyway, thanks!

作者: 猫猫头 时间: 2002-10-29 23:35

我的做法是一种最小的可能性就是从最小的开始你会发现从0-5，其中任何两个想加都<10 所以一定要有7个数字

作者: tongxun 时间: 2002-10-29 23:46

redhat：这就是抽屉原理。

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