| 小明和小强都是张老师的学生，张老师的生日是M月N日，2人都知道张老师的生日是 > 下列10组中的一天，张老师把M值告诉了小明，把N值告诉了小强，张老师问他们知 > 道他的生日是那一天吗？ > 3月4日 3月5日 3月8日 > 6月4日 6月7日 > 9月1日 9月5日 > 12月1日 12月2日 12月8日 > 小明说：如果我不知道的话，小强肯定也不知道 > 小强说：本来我也不知道，但是现在我知道了 > 小明说：哦，那我也知道了 > 请根据以上对话推断出张老师的生日是哪一天 |
6月4日吗？ |
在6月的话，小明不敢说：“如果我不知道的话，小强肯定也不知道” ----万一要是 6月7号呢？所以肯定不是在6月。 |
6月7日 是肯定不会的，虽然我不知道6月4日是否是对的。因为 如果是6月7日的话，小强不用听小明的话就知道了 |
你真幽默..... |
你真幽默...... |
小明和小强都是张老师的学生，张老师的生日是M月N日，2人都知道张老师的生日是 > 下列10组中的一天，张老师把M值告诉了小明，把N值告诉了小强，张老师问他们知 > 道他的生日是那一天吗？ > 3月4日 3月5日 3月8日 > 6月4日 6月7日 > 9月1日 9月5日 > 12月1日 12月2日 12月8日 > 小强说：如果我不知道的话，小明肯定也不知道 > 小明说：本来我也不知道，但是现在我知道了 > 小强说：哦，那我也知道了 > 请根据以上对话推断出张老师的生日是哪一天 |
你更幽默...... |
這個題是俺轉的﹐在網上爭議較多。題很有趣﹐之所以有爭議﹐因為題目沒有象常規的數學題那麼嚴密。 下面是其中一個比較中肯的解答﹕ 作者﹕GMGMGM 整个题的核心就在于小明为什么会对本来就不知道的事情作假设。 |
谢谢，懂了 I believe September 1st is the only right answer.
First of all, it could not be in June. Because if A does not know M, he is sure that B would not know the birthday. So if it was 6/7, no matter what, B knows it was in June. Since A denies that B knows the birthday in A's first sentence, he sends a signal to B that the month of the birthday definitely was not June. "A said If I don’t know, B doesn't know either". So A is sure B doesn't know. If the date is either 2nd or 7th, B would know the birthday under all possible conditions, then this condition prevents A from saying "If I don’t know, B doesn't know either”. Same logic here, it could not be in December either.
So the only possible answers left for B were 3/4, 3/5, 3/8 and 9/1, 9/5. The month could not be 6 or 12. Then B said “I did not know before but now I know”. That tells us, it could not be 3/5 or 9/5, because if it was 3/5 or 9/5, B would still be confused by two 5’s. Then the only answers left for A are 3/4, 3/8, and 9/1. Since we know the month was Neither 6 or 12, so to B, if it was not on 6/4, it must be on 3/4. If it was not on 12/8, it must be on 3/8. If it was not on 12/1, it must be on 9/1. B said now he knows after A said the first sentence. All 3 possible answers were to choose one from two. Deny one answer will automatically push the right answer to the other. Could it be on 3/4 or 3/8 then? The answer is NO NO NO! To A, 3/4, 3/8, and 9/1 are all possible answers from B. However, remember, A finally said, “now I know it too”. If A was told the Month was 3, A would not able to tell the difference from 3/4 and 3/8, because either of them could be B's possible answer. If the month was 3, since we denied month was 6, so we can get 3/4, and we also denied month was 12, so we can get 3/8 as well. So if the month was 3, A could not say "Now I know the birthday". It is because A would have to get 2 possible answers from 4 choices. However, if A was told the Month was 9, and we denied the date was 5, A is sure to say "I know the answer". It is because A can choose one answer from two possible choices.
So A must know 9 was the month, and B must know 1 was the date.
Finally, 9/1 is and one and the only correct answer!
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