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问题| Schnabel |
Posted: February 07, 2006 08:07 am
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Advanced Member  Group: Members Posts: 166 Member No.: 4 Joined: November 01, 2005  |
求把一根筷子折成三段后能够组成一个三角形的概率
12个球其中一个与其他球不同重，请用天平三次分出这个球 |
 
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| xufan |
Posted: February 09, 2006 08:41 am
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Advanced Member Group: BM Posts: 172 Member No.: 3 Joined: August 19, 2005 |
第一个要想的，现在太累的，不想做。 第二个比较简单啦，很小就会了，不过这个比知道坏球是重还是轻的要难一些，但还是可以解决的，呵呵。 先把球编号，1-12，将1 2 3 4与5 6 7 8称（第一次） A）平衡，则坏球在9-12，将1 2 3与9 10 11称（第二次） a）平衡，则坏球是12 b）9 10 11重，9和10称（第三次） I）平衡，则坏球是11 II）不平衡，则坏球是重的那个 c）9 10 11轻，9和10称（第三次） I）平衡，则坏球是11 II）不平衡，则坏球是轻的那个 B）1 2 3 4 重，则坏球在1-8，将1 6 7 8和5 9 10 11称（第二次） a）平衡，则坏球在2 3 4内，2和3称（第三次） I）平衡，则坏球是4 II）不平衡，则坏球是重的那个 b）1 6 7 8重，则坏球是1 c）1 6 7 8轻，则坏球在6 7 8内，6和7称（第三次） I）平衡，则坏球是8 II）不平衡，则坏球是轻的那个 C）5 6 7 8 重，这个和B其实同理，就不写了。 |
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| Schnabel |
Posted: February 10, 2006 07:42 am
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Advanced Member Group: Members Posts: 166 Member No.: 4 Joined: November 01, 2005 |
很牛么你 第二题我想了一星期 不过第一题估计你想不出了，哈哈哈哈哈哈 |
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| xufan |
Posted: February 10, 2006 07:58 am
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Advanced Member Group: BM Posts: 172 Member No.: 3 Joined: August 19, 2005 |
hengji 为什么啊，难道题目有问题？ |
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| Schnabel |
Posted: February 11, 2006 05:33 am
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Advanced Member Group: Members Posts: 166 Member No.: 4 Joined: November 01, 2005 |
no,我觉得你没学过应该做不出的，除非你是高斯一样的数学天才 |
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| xufan |
Posted: February 14, 2006 01:50 pm
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Advanced Member Group: BM Posts: 172 Member No.: 3 Joined: August 19, 2005 |
想过了，ms要概率积分，偶不会做。不过从逻辑上还是大概可以解释的，应该是1/4吧 |
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| Schnabel |
Posted: February 15, 2006 05:32 am
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Advanced Member Group: Members Posts: 166 Member No.: 4 Joined: November 01, 2005 |
不用积分,用解析几何 |
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