Puzzle Corner

I think it actually works out even. 

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Yes there is an imbalance when it's 2 boys and 2 girls. But when it's all girls, it adds up to 12 sisters (each of the 4 girls has 3 sisters). Taking all possible combinations into account adds up to the same number of sisters.

Linda

I did no counter balancing calculations because the parameter of the question was to assume equal split,

"assume each child is equally likely to be a boy or a girl, independently of the sex of its siblings."

so that's what I did. it didn't sound like it was asking for all possible combinations, because if it was, why not just say that?