A family has five kids. Assume that each child has an equal chance of being...

Step 1 
A family has five kids. Assume that each child has an equal chance of being a boy or a girl. If it is known that the family has at least one girl, calculate the likelihood that there are 5 girls.
So, there are 
${\displaystyle 2\times 2\times 2\times 2\times 2}$ (2 raised to the 5th power) 
${\displaystyle =32}$ sequences of 5 children. 
As we already know that only one of them is all female, the probability of five female births in a row when all births are independent and 
${\displaystyle p\left(B\right)=p\left(G\right)=0.5}$ is ${\displaystyle p(G,G,G,G,G)=\frac{1}{32}=0.03125}$ 
Note, that this comes out to be the same as simply multiplying the probability of a girl five times because there is only one of these sequences. if you wanted to know the probability of 2 girls and 3 boys, you have to know how many sequences have 2 girls and 3 boys and adjust accordingly.

You have a $\frac{50}{50}$ chance of it becoming an a boy or a girl.
The chance the first is a girl is 50%. The chance the second is also 50%, and so on.
Therefore the chance that all five are girls is $(0.5{)}^2$ or 3.125%