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.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
条件二缺少了一个总人数,如果有总人数就可以求出common的,25+30+35-16-17-18+x=Total,没了total就求不出x出来
题目问的是交集 不是并集
题目问的是交集 不是并集
A+B+C-AB-AC-BC+ABC=sum
二者/三者既各自独立又有交集的,画饼图解决。
25+30+35-16-17-18+x=total~
(1) 9 即为三者交集。
【图形集合题】
画3个圆,互相相交; 题干AB重合16,AC重合17,BC重合18,
1-9就是ABC三个共有的区域;充分
2-基数知道ABC分别的大小,加上题干的条件也不足以知道公共区域的大小,不充分;
选A
纠正一下楼上,应该是25+30+35-16-17-18+x=total~
条件一绝对可以,但是条件二缺少了一个总人数,如果有总人数就可以求出common的,25+30+35-16-17-18-2x=Total,没了total就求不出x出来