Sorry for bumping this thread but im still stuck. I've given a go at it in finding the pdf.

This is what i have so far:

Basically, if we draw the tree diagram we get a left-weighted binary-tree

We know that we need more girls then boys so we cannot have X = some even number.

Let

be our pdf.

So

, if x is even.

We just need to find the case where X = odd.

I've considered some cases for x = 1,3,5,7,9.....

, this from case {F}

, this is from case {MFF}

, this is for case {MMFFF, MFMFF}

, for cases {MMMFFFF,MFMMFFF,MMFMFFF,MMFFMFF}

**Now**, this is where i get stuck:

for general case:

, for n odd

I'm not sure how to find

. I guess it will be some kind of counting problem and may involve combinations.

Any ideas will be appreciated