Find the probability of at least 2 girls in 10 births. Assume that male and female births are equally likely and that the births are independent events.

Answer 1

The question satisfies requirements for a binomial distribution, where
n=10
p=1/2

Probability of r girls out of n
=P(G=r)
=(n, r)p^r (1-p)^(n-r)
where
(n,r)=combination n choose r
= n!/(r!(n-r)!)

For at least 2 girls out of 10,
P(G>=2)=1-(P(G=0)+P(G=1))
1-(1)(1)(1/1024)-(10)(1/2)(1/512)
=1-11/1024
=1013/1024

Answer 2

.945