Audit Executive
1823 Points
Joined October 2009
1/3 is the correct answer.
since there are 2 boys and 1 girl,the boy and girl ratio is 2:1, which implies that the probability of the fourth child being a girl is 1/3 , that is one girl among three childes.
however if we take the example of a coin then the probability of getting a tail or head is always 1/2, which is unaffected by previous results, according to this principle the answer should be 1/2, since both the problems are identical, but remember the outcome in case of child birth is not definite, there can be even 2 boys or 2 girls i,e twin births !!! there have been cases where count goes even higher !!!
So I strongly go with the first answer, that is, the probability of 1/3 is the correct answer.