A Hillbilly family's only son had saved up money to go to college and after about 3 years he came back home. They were sitting around the dinner table when the dad said, "Well son, you done gone to college so you must be perty smart. Why don't you speak some math fer' us?"
"Ok, Pa", the son said then, "Pi R squared."
After a moment the Dad said, "Why son, they ain't teached ya nothin'! Pie are round, cornbread are square."