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[求助] one interesting question

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11#
发表于 2004-8-22 11:26:00 | 只看该作者

If we have to do this question in a quantitative approach, I choose B.

I assume that Boy (B) and Girl (G) have 50% chance each. Then let's assume that there a sample 1 million families, which should be representative of the population.

Before the policy is adopted, there is no limit on how many children a family has. Therefore B and G should be 50% each because of equal possibility.

With the policy, assume that half (500,000) families have boy and the other half have girl. Then one half with stop and the other half will continue. And it goes on follows:

B 500,000 --> stop
G 500,000 --> 250,000 B ---> stop
                       250,000 G ---> 125,000 B ---> stop
                                                125,000 G ---> 62,500 B ---> stop
                                                                         62,500 G ---> ....(continue the trend)

I have no present knowledge of advanced math. But as this trend continues, we should know that the boy and girl would stay 50% and 50%. Therefore B is correct.

12#
发表于 2004-8-22 12:09:00 | 只看该作者
Thank you, mindfree. It makes sense to me.
13#
发表于 2004-8-23 13:11:00 | 只看该作者
B,应该注意到一胎生男生女的可能性和一个家庭生男生女的可能性,一个国家男女的比率是由这个国家的一胎生男生女的可能性决定的。
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