The doctor was administering a memory test to three old gentlemen.

He asked, "What is 3 times 3?"

The first old man replies, "One hundred and fifty six."

The doctor turns to the second old man.

"What's 3 times 3?"

The second old man says, "Tuesday."

The doctor then turns his attention to the third old man and asks him the same question; 'how much is 3 times 3?'

The third old man answers, "Nine!."

"And just how did you arrive at that answer?" the doctor asks.

The third old man says, "Oh, that's easy, doc! I just subtracted Tuesday from 156 and I got nine."