What do you get if you multiply six by nine?
"Six by nine. Forty two."
"That's it. That's all there is."
"I always thought something was fundamentally wrong with the universe"
Well as most people know, the “answer” to this question (in the Hitchhikers universe) is 42.
When Douglas Adams was asked whether he invented this question because six times nine is actually 54, which is 42 when written in base thirteen, he replied:
"I may be a sorry case, but I don't write jokes in base 13."
Then what was it based in?
As seen in this answer, Doug Adams chose 42 (the answer) randomly:
The answer to this is very simple. It was a joke. It had to be a number, an ordinary, smallish number, and I chose that one. Binary representations, base thirteen, Tibetan monks are all complete nonsense. I sat at my desk, stared into the garden and thought '42 will do'. I typed it out. End of story.
but where did he get the question from?
By question I mean
"What do you get if you multiply six by nine?"
Where did Douglas Adams come up with that question to come out of letters from a Scrabble set? A Scrabble set does not even have all of those letters!