Python 3 explanation of https://math.stackexchange.com/questions/15055/in-a-family-with-two-children-what-are-the-chances-if-one-of-the-children-is-a

child_prob.py

# In a family with two children, what are the chances, if **one** of the children is a girl, that both children are girls?
from random import random
n = 0
c = 0
for i in range(100000):
    a = random() < 0.5
    b = random() < 0.5
    if a or b:  # **one** implies _either_ child
        n += 1
        if a and b:
            c += 1
print(c/n)  # 1/3

# In a family with two children, what are the chances, if **the youngest** is a girl, that both children are girls?
n = 0
c = 0
for i in range(100000):
    a = random() < 0.5
    b = random() < 0.5
    if a:  # Only **the youngest** is a girl
        n += 1
        if b:
            c += 1
print(c/n)  # 1/2