Lottie, my good friend from out west, sent this one...

Three mischievous grandmas were sitting on a bench outside an assisted living facility. About then an old grandpa walked by, and one of the 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 fools."

One of the sly grandmas said, "Sure we can! Just drop your undershorts and we can tell your exact age."

Embarrassed 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 devious grandmas snickered and laughed. Slapping their knees and grinning from ear to ear, all three happily yelled in unison, "Because we were all at your birthday party yesterday!"