请教：两道DS数学

purplehyacinth · 发表于 2010-1-22 08:15:33

1 if X,Y and Z are integer, is X+Y+2Z even?
(1) X+Z is even (2) Y+Z is even
(D)
我明白(1)是对的，但是不明白（2）为何也对，因为不知道X是奇还是偶？

2 Of the 200 members of a certain association, each member who speaks German also speaks English, and 70 of the members speak of Spanish. If no member speaks all three languages, how many of the members speak two of the three languages?
(1) 60 of the members speak only English
(2) 20 of the members do not speak any of the languages.
(C)

purplehyacinth · 发表于 2010-1-22 08:34:16

3 Equal amounts of water were poured into two empty jars of different capacities, which made one jar 1/4 full and the other jar 1/3 full. If the water in the jar with lesser capacity is then poured into the jar with the greater capacity, fraction of the larger jar will be filled with water.
1/7, 2/7, 1/2,7/12,2/3
(C)

我心向明月 · 发表于 2010-1-22 08:53:05

第一题，我选A，为什么选C，求指点
第二题，选C，画图能画出来
第三题，1/2，1/4满的那个瓶子大，再倒进去同样的水，1/4+1/4=1/2

eddycheng · 发表于 2010-1-22 09:09:00

第一个题目，因为是2Z，一定是偶数，这样其实就不用管Z了。X和Y应该是同奇偶，只能联合起来。才可以。

OliverJ · 发表于 2010-1-22 13:04:51

第一题是C 吧同意楼上的

请教：两道DS数学

再来一个！算不出正确答案

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