Unexpected math lesson.

My son wanted to do another experiment from the Big Book of Boy Stuff yesterday.  He wanted to make homemade root beer.  So while I was at the store, I picked him up some root beer flavoring (who knew this even existed?) and some soda water and when we finally got home last night from all our after school activities (9:30 p.m.) the younger 2 kids made root beer.  I didn't expect it but I kept hearing them doing math calculations.  It seems that their syrup was supposed to make 3 cups, but it only made 2 1/2 cups and they were supposed to add 5 ounces of soda water to every 1/2 cup of syrup.  Youngest son wanted to just pour it all in, the whole 32 ounce bottle but the girl wanted to be precise.  I heard them arguing him saying "It's not an exact science!" and her insisting that it was.  Finally I went in and helped them, but we used the girl's math, because she was so determined.  It ended up being a little strong and needing a little bit more club soda added to it, so the boy was right.  For some reason, it smelled like root beer, but tasted kind of like wintergreen life savers.  It was fun anyway.  Today, they are going to do a more old fashioned recipe with that does not have club soda, but instead uses yeast to make the bubbles?  I can't say that sounds appetizing to me.