Back from school

A fifth generation farmer has determined that his son will be the first in their family to go to college. So he and the wife save every penny for years and when the big day comes for junior to leave for school, the old man is the proudest he's ever been.

After the first semester junior comes home for Christmas break and the old man sits him down for a talk. "Well, boy, you been at school for three months now, I want you to tell me some of that fancy book learnin'."

So junior says, "My favorite class is math, pa. Just last week we learned a new formula...Pi r squared."

At hearing this the old man screws up his eyes and smacks his forehead, "Dog gone-it! I spent all that money on schooling and all you can tell me is Pi r squared? Why everybody know pie are round...CORNBREAD are squared!"