C.C.
The size of raw potatoes is variable. I tend to cook about three fist-sized potatoes for each of us, and I eat less than they do. There's seldom any left. With a meal, my teenaged sons can each easily eat a portion of mashed potato sufficient to fill a cereal bowl. One of them will also be looking for seconds. They also eat more when their friends are around. I think it's partly because they enjoy the conversation and want the meal to continue, and partly because they have always seemed to feel that mealtimes are a competition in which the one who gets the most food is the winner.