请问一道数学题？

weiyihantime

There are 1,200 respondents in a survey. And they are divided into three groups, such as A, B and C with percentage of 54%, 36% and 42%(数字抄的梦飞翔的，感觉好像有点出入) respectively (numbers may not be accurate). The percentage of A and B is 30%, what is the maximum number of C that is neither in A nor B.
                我选的312，比较确定，算了两遍。
 怎么算的阿？十分感谢哦“）

weiyihantime

另外请问计算式 7^-1/42^-8=中的符号^是什么意思啊

 

chenzheng

^ 是平方的意思

njkobe

这题看过好多遍了～第二个数字肯定错了～是48%不是36%～算法如下
第一题问C最多就是说那30%全为A或B且和C无交集,so:
56-30=26
48-30=18
26+18+30=74
1200*(1-.74)=1200*.26=312

yjz809

发现一个很有趣的现象

A+B+C-AB-AC-BC+ABC=1, and C-AC-BC+ABC = Ans

so Ans = 1-A-B+AB, regardless of overlap between C and A/B

不知道我有没有想错。。。