Question

Find the probability that when a couple has three children, at least one of themis a girl. (Assume that boys and girls are equally likely.)

Answer 1

Answer:
`\bold{(7)/(8)=87.5\%}`

Explanation:

"At least one girl" means P(1 girl) + P(2 girls) + P(3 girls) or 1 - P(all boys)

I will use the latter: 1 - P(all boys)

P(all boys) =
`(1)/(2)* (1)/(2)* (1)/(2)=(1)/(8)`

`1 - P(all\ boys) \quad = \quad 1-(1)/(8)\quad =\large\boxed{(7)/(8)}`