one JJ

cook

2.A flower arrangement A have 3 red , x White flowers; a flower arrangement B have 5 red, 3 white flowers, ask for X:
(1)IF a flower draw from each arrangement , the probability of two flowers are both red is 1/6;
(2)IF a flower draw from each arrangement , the probability of two flowers are both white is 9/40;

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My answer is D correct?

nan

我不知道又是哪根神经搭错位了，我怎么从(1)和(2)里推出的X都不是整数呢？？？
有人能把方法列出来吗？

tuantuan

就是不是整数啊，答案是E吧。
我的方法是1. (C3 1)*(C5 1)/(C3+x 1))(C8 1)=1/6
          2. (Cx 1)*(C3 1)/(C3+x 1))(C8 1)=9/40

cook

Be careful about the digits, the method to solve the problem is correct, I think. thanks!