p(0g) = 1/2. (Probability of no girls)
p(1g) = 1/2^2 (Probability of exactly 1 girl)
p(2g) = 1/2^3. (Probability of exactly 2 girls)
p(3g) = 1/2^3. (Probability of exactly 3 girls)
Expected number of girls = 0*1/2 + 1*1/2^2 + 2*1/2^3 + 3*1/2^3 → 7/8
p(0b) = 1/2^3
p(1b) = 1/2^3 + 1/2^2 + 1/2 → 7/8
Expected number of boys = 0*1/2^3 + 1*7/8 → 7/8
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