Answer:
The probability of every simple event is:
P(B)=0.5
P(GB)=0.25
P(GGB)=0.125
P(GGGB)=0.0625
P(GGGG)=0.0625
Step-by-step explanation:
For simple event B, the probability is calculate as have a boy in the first birth, so: P(B)=0.5
Then, for the event GB, the probability is calculated as the multiplication of the probability of have a girl in the first birth and have a boy in the second, so:
P(GB)= Â Â Â 0.5 Â Â Â Â * Â Â Â Â 0.5 Â Â Â =0.25
      have a girl   have a boy
At the same way for the event GGB, the probability is calculated as the multiplication of the probability of have a girl in the first and second birth and have a boy in the third, so:
P(GGB)=0.5*0.5*0.5=0.125
For the event GGGB, the probability is calculated as the multiplication of the probability of have a girl in the first, second and third birth and have a boy in the fourth, so:
P(GGGB)=0.5*0.5*0.5*0.5=0.0625
Finally, for the event GGGG, the probability is calculated as the multiplication of the probability of have a girl in the first, second, third and fourth birth, so:
P(GGGG)=0.5*0.5*0.5*0.5=0.0625