Ok, the question is If a couple plans to have 10 children what is the probability of having at least one girl?

This is a homework question. I do not want the answer. All I would like to know is if I am getting this formula correctly and if not, what is the process I need to do in order to obtain a correct answer. I have midterms in a few weeks and would really like to understand this formula. Thank you for your time and help, it is greatly appreciated.

Ok so if I understand this correctly then...

A= 1/10 or 0.1 (At least 1 of the 10 children is a girl)

The complement of A (A`) is: All 10 children are boys

1/9 * 1/9 * 1/9 * 1/9 * 1/9 * 1/9 * 1/9 * 1/9 * 1/9 = 0.000000003

P(A)= 1 - P(A`) = 1 - 0.000000003 = 0.999999997

So there is a 0.999999997 probability that if a couple has 10 children, at least one of them is a girl.

The best way to approach a 'at least one' problem is to calculate the probability of none and subtract from 1.

So, what is the probability of no girls, then subtract from 1.

This is a binomial probability.

1-C(10,0)(.5)^{0}(.5)^{10}