Solution.txt

github.com/RodneyShag


Answer: 1/3

****** 2 valid answers: 1/3 or 1/2

Reference: https://en.wikipedia.org/wiki/Boy_or_Girl_paradox

This question is known as the "Boy or Girl Paradox". The actual answer is either 1/3 or 1/2 
depending on how the question is interpreted. Here are 2 ways to interpret the question:

1) From all families with two children, at least one of whom is a boy, a family is 
   chosen at random. This would yield the answer of 1/3.
2) From all families with two children, one child is selected at random, and the sex 
   of that child is specified to be a boy. This would yield an answer of 1/2.


******* Interpretation (1) gives an answer of 1/3

There are 4 possible scenarios: (B, B), (B, G), (G, B), (G, G)

We know that 1 child is a boy, so now we have 3 scenarios: (B, B), (B, G), (G, B)

When asked, "what is the probability that both children are boys", the only scenario that 
matches this is: (B, B). That is, only 1 of the 3 scenarios satisfies the critera, so 
there is a 1/3 chance that both children are boys.


******* Interpretation (2) gives an answer of 1/2

In this scenario, a child was selected at random from a set of all children that have 
exactly 1 sibling. Knowing the fact that the child is a boy does not give us any 
information on whether his sibling is a boy or a girl. 


******* HackerRank's correct answer

The accepted answer on HackerRank is 1/3. This aligns with the fact 
that the problem wording more closely resembles Interpretation (1).