Okay... Let's not ruin the hitchhiker here.. the answer: 42; The question 6x9; Reply: I always thought something was fundamentally wrong with the universe.
DA leaves it as a conundrum, but I'm SURE that it's not supposed to be any -error- in the question (or answer), It's supposed to be a source for further thinking.. DA often tries to make us think.
If I am going to give ONE of the way of thinking where the sum of a correct equation is different from reality.. The universe is supposed to not have existed.. just a great nothing.. and as we all know; nothing comes from nothing.. and yet, the university, AND matter is supposed to suddenly appear from it.. Possible explanation (of which DA's equation should be considered a simplified form of):If we were to form a great unification theory which would not only explain the fabric of space- as we know it- but also about the non-space- as it was before space existed- we would find out the the sum of non.space was "zero" evenly distributed, but there was suddenly a disruption in the "scattering" of the balance (6*9 suddenly became 42) which meant that there was something that "subtracted" at one point and "added" at another (total sum still zero) which the "chemistry" of the non-space could not resolve in other way than creating energy (which turned to matter and time)
A more philosophical way of looking at it; We are not supposed to make sense.. we can have pieces of the puzzle, but even if we have (what we believe to be) complete question, and answer, we still have missunderstood how to use those to actually get the answer we thought we were searching.
Six times nine is, of course, fifty-four. The program on the "Earth computer" should have run correctly, but the unexpected arrival of the Golgafrinchans on prehistoric Earth caused input errors into the systemâ€”computing (because of the garbage in, garbage out rule) the wrong questionâ€”the question in Arthur's subconscious being invalid all along.
Therefor the answer to the ultimate question of life, the universe, and everything is still unknown.