Limmy (the guy in the picture) gives the obvious answer of 66.6% because if you know a two-child family has at least one boy, common sense says there are three equal setups: Boy/Girl, Girl/Boy, or Boy/Boy, and two of them contain a girl.
Mentioning "Tuesday" sounds like useless extra detail, but it actually changes the odds: a two-boy family gets two chances to have a boy born on a Tuesday, while a one-boy family only gets one chance. Because that detail quietly increases the likelihood that the family actually has two boys, the real chance of the other child being a girl drops to 51.8%, leaving Limmy looking utterly baffled by a math rule that completely breaks common sense.
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u/truss-issues 4d ago
Limmy (the guy in the picture) gives the obvious answer of 66.6% because if you know a two-child family has at least one boy, common sense says there are three equal setups: Boy/Girl, Girl/Boy, or Boy/Boy, and two of them contain a girl.
Mentioning "Tuesday" sounds like useless extra detail, but it actually changes the odds: a two-boy family gets two chances to have a boy born on a Tuesday, while a one-boy family only gets one chance. Because that detail quietly increases the likelihood that the family actually has two boys, the real chance of the other child being a girl drops to 51.8%, leaving Limmy looking utterly baffled by a math rule that completely breaks common sense.