一道数学题 百思不得其解。。

dandanapple

the probability of a is 60% and the probability of b is 50%, what is the most possible probability that neither a nor b would happen?  

(a) 0.80  
(b) 0.40  
(c) 0.75  
(d) 0.55
(e) 0.68

答案是0.4，百思不得其解，求大家帮忙呀！

onedayling

我猜测 A和B不是独立的，因此 A不发生0.4，B不发生０.５，　A,B均不发生的最大的possibility就是０.４了

dandanapple

有道理有道理！
这道题的关键是不是要理解0.6+0.5大于1， 所以二者一定有交集呢？这样的话就容易想清楚了。

xiangrui

u might use the graph to help, it would be much easier for you to figure out the answer.
assume the A includes B , so you would get the "maximum possibility of neither A nor B" is 0.4
so here you only can choose 0.4 to be the answer.