Riddle #766

Question: Mr. Smith has two children. If the older child is a boy, what are the odds that the other child is also a boy?

Origin: http://en.wikipedia.org/wiki/Boy_or_Girl_paradox

Riddle Discussion

By: nashlover007 on 13/6/16


By: DeathTheKidRinO on 25/4/16

This is incorrect. It would actually be 1/3, and I will work it out here:\n\nHere are the 4 combinations\nGirl, Girl\nBoy, Boy\nGirl, Boy\nBoy, Girl\n\nNow, since we know that there is at least one boy, the first combination, Girl; Girl, is not possible. This leaves three combinations left ( Girl; Boy, Boy; Girl, and Boy; Boy). Only one of the three possible combinations is two boys, leaving the answer 1/3.

By: hirogaems on 2/7/16

I was also thinking that it was incorrect, but for a different reason: odds aren't given in the form of a percentage. The answer should be 1:2. The reason that it is 1:2 or 50%, though, is that Boy, Girl and Girl, Boy are equivalent. If you know that one of the kids is a boy, Girl, Girl is eliminated and you're left with Boy, Girl and Boy, Boy. It's a coin toss. If you stipulate that the order you list the possibilities in is linked to their order of birth, you can then include both Boy, Girl and Girl, Boy... but then once you know the first born was a boy, you still have to get rid of Girl, Boy and Girl, Girl. You're still left with a 50/50 chance that the second child is also a boy.

By: DeathTheKidRinO on 25/4/16

Okay, this was my first comment on this website, and I did not know that you cannot use the enter key without getting a bunch of crap... Please do not mind the horrid, terrifying "\\n"s that replace the areas where I meant to move down a line.

By: louisedmh on 20/4/16


By: cadstengaming on 19/3/16


By: RiddleMastery on 17/1/16

Is this a riddle for children? It is even hard for me lol

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