作者fly12404 (郭品超)
看板GMAT
标题Re: [问题] PP计量问题
时间Wed May 7 01:01:04 2008
12. 781-!-item-!-187;#058&000341
Sets A, B, and C have some elements in common.
If 16 elements are in both A and B, 17 elements are in both A and C,
and 18 elements are in both B and C,
how many elements do all three of the sets A, B, and C have in common?
(1) Of the 16 elements that are in both A and B, 9 elements are also in C.
(2) A has 25 elements, B has 30 elements, and C has 35 elements.
20+30+35-16-17-18-2(ABC)=25+30+35
^^你这20不知道哪来耶!?
ABC算出来不是整数 所以(2)不行 是这样所以不充分吗
列式解题方向是这样吗?
正确的公式应该是 N(A U B U C) = N(A)+N(B)+N(C)-N(A^B)-N(A^C)-N(B^C)+2N(A^B^C)
我们无法得知 N(A U B U C) 即使後面的数字皆有
仍无法算出N(A^B^C)
这是我的想法 Q Q
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 140.115.200.29
1F：推 yhubi:算是後面应该是 -N(A^B)-N(A^C)-N(B^C)+N(A^B^C) 这样吧?? 05/07 11:03
※ 编辑: fly12404 来自: 140.115.200.29 (05/07 13:14)
2F：→ fly12404:哈~打太快哩! 不过跟我原本想法一样 05/07 13:14
3F：→ fly12404:还是一样 +2N(A^B^C) 喔 05/07 13:15