求解答

maerchen

In each production lot for a certain toy, 25 percent of the toys are red and 75 percent of the toys are blue. Half the toys are size A and half are size B. If 10 out of a lot of 100 toys are red and size A, how many of the toys are blue and size B?


求问，这道题为什么不可以用25%＊50％＝1/8，先算 red and size A toy 的概率，然后10/(1/8)=80,80*75%*70%=30?

lzc95232

红和蓝，A和B是两种集合，可以用这个集合的概率乘另一个集合的概率来算吗？如果同时在一个集合中是100%是可以的吧，这样是不是相当于一共是200%了