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标题: 请教一道PREP的数学题 [打印本页]

作者: sabineceng 时间: 2013-3-2 21:44 标题: 请教一道PREP的数学题

6、if there are more than 2 numbers in a certain list,is each of the numbers in the list equal to 0?
(1) the product of any 2 numbers equal to 0
(2)the sum of any 2 numbers equal to 0

答案是B

不明白为什么条件1不sufficient

谢谢：）

作者: buaagonggan 时间: 2013-3-3 08:43

比如举三个数：3、0、0 任何两个数相乘都等于0啊，但并不是每个数都为0的

作者: sabineceng 时间: 2013-3-4 06:44

对哦谢谢啦茅塞顿开
再问一道：26. Tanya Tanya prepared 4 different letters to be sent to 4 different addresses. For each letter, she prepared an envelope with its correct address. If the 4 letters are to be put into the 4 envelopes at random, what is the probability that only 1 letter will be put into the envelope with its correct address?
A、1/24
B、1/8
C、1/4
D、1/3
E、3/8

希望有找到的童鞋再次帮忙，感谢！！

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