When you know for sure, that a kid is Boy, why would you give it a 1/2 probability again. Though there are 3 kids, you know for sure one is a boy.
What you did would be right if you didnt know if the first kid was a boy or a girl, in that case you could do;
(1+3)/8 = 4/8 (Not sure why the denominator is 7 in your Ans)
dwarzoha001 wrote:How I look at the question is this:
Chances of the three kids being:
GGG: 3!/3! = 1
GGB: 3!/2! = 3
GBB: 3!/2! = 3
BBB: 3!/3! = 1
The question states that there is already one boy, so you know GGG is not an option. So then I would just add the GBB and BBB scenarios over total possible and get [spoiler]4/7.[/spoiler] Please advise.
