Out of 800 families with 5 children each, how many would you expect to have 3 boys. Assume equal probability for boys and girls

Answer 1

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Prob( exactly 3 boys)

(5 choose 3) * (1/2)^3 (1/2)^2

10 * 1/8 * 1/4 = 10/32 = 5/16

note that there are 10 out of 32 combinations highlighted in bold above, containing exactly 3 boys.

5/16 * 800 = 4000/16 = 2000/8 = 1000/4 = 250