Three mischievous grandmas were sitting on a bench outside of their nursing home, laughing their heads off like giggling girls.

“Now, now, ladies,” a nurse said, walking past them. “You need to get your sunshine time before tea. And behave!”

Her words only set them off again. Soon, they spotted an old man walking by and decided to have a bit of fun with him.

“We bet we can tell exactly how old you are,” one of the grandmas yelled out at him.

The old man scoffed.

“There’s no way that you can guess it, you three old fools.”

“Sure we can!” another grandma insisted. “Just drop your pants and we can tell your exact age!”

“What?” he exclaimed.

Embarrassed but intrigued, the old man dropped his pants, the sunlight shining on his bottom.

The grandmas stared and whispered among themselves. And then said in unison, “You’re 91 years old!”

“How in the world did you guess?” the old man asked, shocked.

The grandmas snickered and replied,

“Because we were at your birthday party yesterday!” one grandma said as the other two collapsed into giggles again.