What is the Probability of Having a Girl as the Third Child?

[Petenerd]

I need help with this question:

A woman gives birth to a son. Two years later, she gives birth to another son. What is the probability that her third child will be a girl? Explain your reasoning.

I think it is 50% chance that it will be a girl because when you use the punnet square the outcome of the combination is 50%. I'm not sure if this is correct.

 

[ideasrule]

I don't know why you need to do a Punnet square. The chance that your baby will be a girl is 50%, period. The sperm that are swimming up the vagina and competing with each other to fertilize the egg couldn't care less about the sex of the woman's previous children.

 

[wintrymei]

Your punnett square results are correct - the gender of a child is always 50% male and 50% female. Previous births don't affect probabilities.