Class - boys and girls

In the class are 60% boys and 40% girls. Long hair has 10% boys and 80% girls.

a) What is the probability that a randomly chosen person has long hair?
b) The selected person has long hair. What is the probability that it is a girl?

Result

p₁ =  0.38
p₂ =  0.842

Solution:

$p_1 = 0.1\cdot 0.6 + 0.8\cdot 0.4 = 0.38$

$p_2 = 0.8\cdot 0.4 / p_1 = 0.842$

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