Question 267277
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If the second child is a girl, the only possible way to have two boys in a total of three children is for the first and third to be a boy.  Since we are presuming that it is still possible after the first two children are born to have two boys in a total of three children, then it is certain that the first is a boy.  Hence, the probability of the couple having exactly three children is the same as the probability that the third child is a boy, that is, 0.5



John
*[tex \LARGE e^{i\pi} + 1 = 0]
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