And because the number of children in each family is different, X; =3, so x = 3,4,5,6.
We found that when x = 5, for four families with small numbers, the number of children is at least 1, 2, 3, 4. In other words, the fifth family has at least 1 1 children. In this way, the total number of children is at least 2 1, which is twice as much as the total number of adults. Obviously, it is inappropriate. That is to say, x can only be 3 and 4.
Since all girls have brothers, there must be only one boy in the one-child family. And the number of girls in a family does not exceed two.
therefore
1 and X=3, then y = 4 and z = 5.
There are ***9 children, so the family with the most children has 5 children, and the other 2 families have 4 children, so 1 family has 1 child, 1 family has 3 children, 1 family has 5 children. Because girls have at least one brother and at most one sister, 1 family has only one boy, and the other two families have two girls, that is, the first family has 1 boy, the second family has 1 boy and two girls, and the third family has three boys and two girls.
2, X=4, then Y=5, Z=6, 7 Y=6, Z=7.
Consider y = 5 and z = 6. Because the family with the most children needs more than half, that is, at least six children, while the remaining three families have at most five children. No matter how children are distributed, families with the same number of children can always appear in 1 13 and 122. Y = 5, z = 7.
Similarly, when x = 5,6, there will always be families with the same number of children.
When y = 6 and z = 7, the maximum number of children in one family is 7, and the number of children in the other three families is 1, 2 and 3 respectively. Because the total number of boys is less than 8 of the total number of adults, we consider the problem from the perspective of considering the least number of boys, that is to say, there are 1 boys in family A, 1 boys in family B, 1 girls in family C, 1 boys and 2 girls in family D. In this way, the total number of boys is 1+ 1+ 1+5 = 8, which is equal to the total number of adults, so it is discarded.
So there are three families, the first one is 1 boys, the second one is 1 boys and girls, and the third one is 3 boys and 2 girls.