我问一个可能比较简单的问题:呵呵,哪位帮忙解答一下,多谢~~
新东方绿皮书 Problem Solving no.343
If the sum of a set of ten different positive prime numbers is an even number, which of the following prime numbers CANNOT be in the set?
A 2 B 3 C 5 D 7 E 11
answer: A
因为除了2其他的质数都是奇数。
9个奇数的和还是奇数,那么第10个数必然是奇数,所以不能是2
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