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Homework Help: Probablity of the next child?

  1. Dec 10, 2009 #1
    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.
  2. jcsd
  3. Dec 10, 2009 #2


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    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.
  4. Dec 15, 2009 #3
    Your punnett square results are correct - the gender of a child is always 50% male and 50% female. Previous births don't affect probabilities.
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