Three old mischievous grandmas were sitting on a bench outside a
nursing home. About then an old grandpa walked by, and one of the old
grandmas yelled out saying, "We bet we can tell exactly how old you
are."

The old man said, "There ain't no way you can guess it, you old
fools."

One of the ornery grandmas said, "Sure we can! Just drop your under
shorts and we can tell your exact age.

Embarrassed just a little, he dropped his drawers. The grandmas stared
at him for a while, asked him to turn around a couple of times, asked
him to jump up and down for a little while and then they all piped up
and said, "You're 84 years old!"

"How in the world did you guess?!?"

The ornery old grandmas snickered and laughed. Slapping their knees
and grinning from ear to ear, all three happily yelled in unison,

"Because we were at your birthday party yesterday. "