very basic doubt

[mehaksal]

What is the probability for a family with three children to have a boy and two girls (assuming the probability of having a boy or a girl is equal)?

a) 1/8
b) ¼
c) ½
d) 3/8
e) 5/8

I did tend to go this way :-
as only possibilities are 3G, 3B, 2G & 1B, 2B & 1G,
hence, 1/4, without going through 1/2 for boy and girl types...
I know this approach is very wrong, please help me in clearing such a basic doubt

[Ian Stewart]

1/4 isn't correct because it's more likely you'll have, say, 2 boys and 1 girl than it is that you'll have 3 boys. One (long, but easily manageable in two minutes) way to do the problem is to list all of the possible sequences of boys and girls:

BBB
BBG
BGB
GBB
BGG
GBG
GGB
GGG

There are 8 sequences, and in 3 of them we have exactly two girls, so the answer is 3/8.

There are faster ways to do these problems, which have been posted in this forum before, so I won't repeat them, but you might search for Stuart Kovinsky's post from a couple of years ago called something like "coin flip problems made easy".

[mehaksal]

I understand the logic here, but does the sequence matter as well in this question?
I mean 2B and 1G can be in any sequence, so we consider only BBB,GGG,BBG and GGB..wt do u say abt it?