370.Boy–Girl Neighbors
★★★expected valueCh. 1 — Classical Probability and Combinatorics444+ Problems in Probability
There are 15 boys and 10 girls in a class. They line up in a row in random order. What is the expected number of adjacent boy–girl pairs? (E.g. has 7 such adjacencies.)
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Linearity over the 24 adjacent position-pairs: what is the probability any given pair is mixed?
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