Acording to the scientists who study string theory, the answer to life, the universe, and everything is 10. And 26.
Ah, but 21 minus 10 is 16. Add the digits and you get 7. Adams was probably familiar with the game of baccarat, in which tens (and face cards) are worth zero. So drop the 1 from the 16 and you have 6. 6 x 7 = 42.
Typo. The numbers in the OP were 10 and 26. 26 - 10 = 16.
What do you get when you multiply 10 by 26?
Forty-two.
Ah, I see. Two numbers, hence you can multiply one by two. But then you don’t get to mention baccarat! (Which has nothing to do with anything, but you get to drop the 1 from the 16 
)
I always knew there was something fundamentally wrong with the universe.
In the book, the question is “what is six multiplied by nine?”.
It was intended to be nonsense as well, but some people have argued it means that God has 13 fingers.
If the answer to life is already 10 and 26, why can’t it be 42 as well?
Also, my immediate thought at being told there are 10 dimensions was “how could this be used as a superpower?” Maybe I need to stop reading comic books for awhile…
(“How does your power work?”
“Well, you see, in string theory…”
“Never mind.”)