询问一道数学题，题目看得不是很懂。求解释

pzychloe

If there are more than two numbers in a certain list, is each of the numbers in the list equal to 0 ?
(1)  The product of any two numbers in the list is equal to 0.
(2)  The sum of any two numbers in the list is equal to 0.

我没有看懂问题什么叫做each of the numbers in the list equal to 0?
不是寂静的题，是prep2012 的题。谢谢啦

pzychloe

额。。看懂了。 就是问所有数字是不是都是零。。。。

hermione919

这道题选什么呢？

zdn

我认为是C

kristy16s

我觉得是选C。
问： is each number on the list equal to 0,只要充分否定或者充分肯定就可以了吧。
1. 任意两个数乘积为0，可能都为零，也可能一个0 一个不为0，不充分
2. 任意两个数的和为0，可能一正一负，可能都为0，不充分
所以选c 都为零才能充分

写出来才发现是C，之前乍一看还觉得是D

miushock

B

注意数列长度大于2，条件1可以是全零数列或者任意非零数字和一堆零组成的数列，两种情况都满足任意两个数的积都为零，条件2则要求必须是全零

pzychloe

这题答案是B

jacksontg

B

(1)  The product of any two numbers in the list is equal to 0.
The list could be ... 0,0,1,0,0 ... not sufficient

(2)  The sum of any two numbers in the list is equal to 0.
Since there are more than two numbers in a this list, if the sum is 0, it must be that all the numbers in the list are 0 - So it is sufficient by itself.

ASChen

感谢分享！