A man and a woman have three children: two girls and one boy. The couple decides to have a fourth child. What is the probability that their fourth child will be a girl?

Answer: 50%

Explanation: In the creation of the fetus, chromosomes from the sperm of the male and chromosomes from the egg of the female are joined. Both man and woman have two sex cell chromosomes, with the woman having both X chromosomes and the man having one X and one Y chromosome.

If the X chromosome from the sperm joins the X chromosome from the egg, it means that the fetus has two X chromosomes, as a mum has it, then it will be a girl. If the sperm chromosome Y joins the X chromosome from an egg then the fetus will have one X and one Y chromosome, as daddy has, then it will be a boy. This means that a man i. e. his chromosome affects the gender of a child.

Still, scientists say that equal percentages can vary based on many factors. For example, the Y chromosome is slightly smaller than the X chromosome, and therefore more mobile and faster, so it can reach the egg more easily. Then diet and lifestyle can also change the equal percentage i. e. equal chance, so it can vary by 50%. But again scientific evidence shows that the germ cells do not have the capacity of memory, that is, they do not remember which sex of the child was at the last fertilization of the egg, so with the small deviations noted, the chances are approximately always 50 %.