Two children
Probability
Level
2
A mathematics student is chatting with his professor. The professor says, "I have two children. At least one of them is a boy."
What is the chance that both the professor's children are boys?
1
1/2
1/4
1/3
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1 solution
Letting the older child be first, there are four possibilities, where B = boy and G = girl: GG, GB, BG, BB. Hearing "at least one of them is a boy" eliminates GG: that leaves 3 possibilities, of which 1 yields 2 boys.