A newly wed couple was hosting their first Easter dinner for the wifes family. After watching his new wife Joan slice an inch off of each end of the Easter ham, Bob, the husband asks, "So why do you cut off each end of the ham?" Joan replies "Well, thats how my mother always did it."
Some time later, Joan's mother Mary arrives and the husband says to her, "I was watching Joan prepare the ham and she cut an inch from each end. When I asked her why she did that, she said it was because you always did. So tell me, why do you cut off each end of the ham?" To which Mary replies, "Well, thats how my mother always did it."
Seeing that grandma has already arrived Bob heads across the room to where grandma is, knowing this is his last chance to get to the bottom of this "cutting" question. Bob explains to grandma that he watched Joan cut off the ends of the ham and that she said she does it because her mother did it that way, and Mary said she cut off the ends because you did it that way.
"So tell me" says Bob, "why do you cut an inch off each end of the ham?" Grandma replies, "Well, my pan was too short".