2009-04-05, 05:23 PM
The problem with the people responding 50%, is that they are counting one option twice.
Consider the order.
When the child that is known to be male is born first
B / G
B / B
When the child that is known to be male is born second
G / B
B / B
However, the "B / B" option has already been covered in the scenario when looking at the first child being male, e.g. B / B.
Discounting this gives 3 possible outcomes
B / G
B / B
G / B
All of which are equally likely to happen. Therefore, its 1/3 chance or 33%.
Consider the order.
When the child that is known to be male is born first
B / G
B / B
When the child that is known to be male is born second
G / B
B / B
However, the "B / B" option has already been covered in the scenario when looking at the first child being male, e.g. B / B.
Discounting this gives 3 possible outcomes
B / G
B / B
G / B
All of which are equally likely to happen. Therefore, its 1/3 chance or 33%.