Probability of getting least two girls

Question

A couple plans to have three children(single births).How many possible arrangements of boys(B) and girls(G) are possible?

Write all the possibilities.Assuming all these arrangements are equally likely, explain how to find the probability the couple will have at least two girls.  

Answer 1

The posssibilities are:

BBB

BBG

BGB

BGG *

GBB

GBG *

GGB *

GGG *

There are 8 possible arrangements of boys and girls.

The indicated outcomes have at least two girls, counting those we see there are 4.

P(at least two girls) = 4/8 = 1/2