Name: Bill

Who is asking: Parent
Level: All

Question:
If a family has four children, what is the probability that all 4 are the same sex?



Hi Bill,

We can list all possible outcomes. Here, for example, outcome BGBG means that the oldest in the family is boy, after this girl, then boy again and the youngest is girl. So a list of all possible outcomes is

BBBB     GBBB
BBBG     GBBG
BBGB     GBGB
BBGG     GBGG
BGBB     GGBB
BGBG     GGBG
BGGB     GGGB
BGGG     GGGG

We have 16 possible outcomes, from which only two satisfy your requirement: MMMM and GGGG. So, the answer is  2/16 =  1/8.

Andrei
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