标题: 一道prep数学DS题。。求大神解答。。 [打印本页] 作者: spinyfox 时间: 2012-7-9 18:56 标题: 一道prep数学DS题。。求大神解答。。 If w, x, y, and z are integers such that w/x and y/z are integers, is w/x + y/z odd? (1) wx + yz is odd. (2) wz + xy is odd.
1）肯定不对的，wx+yz is odd, one is even and the other is odd. The product of two is odd, that means both are odds. The product of two is even, that means one or both are even. So you cannot conclude that the sum of all four is odd.
2) is the same
If you combine all the criterea, that means among the all four, one is even, and the rest are all odds. And ths sume is odd.
That's why I choose C...作者: spinyfox 时间: 2012-7-10 01:21
实在不好意思之前有式子没粘上来。。。。不好意思。。