问一道数学题排列组合的

沉睡的蜗牛 · 发表于 2011-11-19 08:26:30

Each of the integers form 0 to 9, inclusive, is written on a separate slip of bland paper and the ten slips are dropped into a hat. If the slips are then drawn one at a tim
e without replacement, how many must be drawn to ensure that the numbers on two of the slips drawn will have a sum of 10?
谢谢

啸啸 · 发表于 2011-11-19 11:17:26

同问~顶

cloudballoon · 发表于 2011-11-19 12:05:17

7 times~

cloudballoon · 发表于 2011-11-19 12:08:20

我对题目的认知是抽出多少纸<不放回> 里面有两个相加一定会等于10

抽多少次一定有的情况下，应该假设都是抽到最小的数字

0123456

所以抽到第七次就一定有了

问一道数学题排列组合的

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