根据我国实行的计划生育政策,提倡少生孩子.假设国家有这样一个规定,如果一对夫妇第一胎生男孩,则不允许生第二胎,如果第一胎生女孩,则允许生第二胎,而且最多生两胎.那么这样的情况,生男孩和生女孩的人数平衡吗?解决此类问题,要用到我们所学的概率及数学期望知识.解设第一胎生 According to the family planning policy implemented in our country, the government advocates the birth of children. It is assumed that the country has such a provision that if a couple has a first-born child, it is not allowed to have a second child. If the first child has a girl, a second child is allowed. And up to two births. Then the situation, the number of boys and girls are balanced? To solve this problem, we must use the probability we have learned and the knowledge of mathematical expectations. Solution for the first birth.