There are 32 possible outcomes (GGGGG, GGGGB, GGGBG, etc).
One of those possibilities is all girls.
One of those possibilities is all boys.
Five are four girls, one boy (GGGGGB, GGGBG, GGBGG, GBGGG, BGGGG).
Five are four boys, one girl.
Of the twenty remaining possibilities, half will be three girls, two boys, while the other half will be two girls, three boys.
You could also make an organized list...
GGGGG
GGGGB
GGGBG
GGGBB
GGBGG
GGBGB
GGBBG
1) GGBBB
GBGGG
GBGGB
GBGBG
2) GBGBB
GBBGG
3) GBBGB
4) GBBBG
GBBBB
BGGGG
BGGGB
BGGBG
5) BGGBB
BGBGG
6) BGBGB
7) BGBBG
BGBBB
BBGGG
8) BBGGB
9) BBGBG
BBGBB
10) BBBGG
BBBGB
BBBBG
BBBBB
You could also make a tree diagram outlining the possibilities.
There are other ways to go about it, too, that aren't quite as labor-intensive, but these are some of the first ways you'd be likely to see.
Either way, it comes out to 10/32, or 5/16, or 0.3125, or 31.25%
