What's the probability that in three children 1 is a girl. It was asked that what is the probability that only one is a girl in a group of 3 children.
My sample space:- 
B B B 
B B G 
B G G 
G G G 
What my friend says:-
B B B 
B B G 
B G B 
G B B 
B G G 
G G B 
G B G 
G G G 
He says it will be like the when 3 coins are tossed. But I say that BBG and BGB are same. So there will be only 4 total outcomes.
Am I correct? Because if we see logically, then probability of one girl is 1/4. Because 1 girl is one girl, whether she is at left or right or middle.
And it is different from the 3 coins that we are tossing.

Sample space alone is not enough to calculate probabilities. To begin with, before selecting the sample space, you need to specify probabilistic experiment, and only after that you have information which sample space to select. Note that we did not assign probabilities yet, that will be the next step.
The question may look good in natural language, but it is lacking necessary information to convert it to math problem.
