Overview
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Here's a three-part puzzler. For each part list the sample space. Listing the sample space will make the probability clear. You can denote Boy as B, Girl as G, and Florida as F when listing a sample space. For example, the sample space of the birth events boy-girl and girl-girl is {BG, GG}.
a) Your friend has two children. What is the probability that both are girls?
b) Your friend has two children. You know for a fact that at least one of them is a girl. What is the probability that the other one is a girl?
c) Your friend has three children. One is a girl named Florida and one is a girl named Holley. What is the probability that the first child is a boy?