not sure if answer above get the point. number is not important here. it is how you think. I would divide US population into two groups based on age 10 to 40 eats more fast food, others eats less. and big-mac is big (right?), so I assume only male buy it. 14 meals a week, I would assume 10-40 group eat 5 fast food a week, and 1 of them is Mcdonalds given so many brands available, which makes 1 mcdonald a week; other age group I assume 0.5 mcdonald a week. When you are at mcdonald, you have many choice and certain percentage goes to big-mac.....

100 billion