I was watching this yesterday evening. Something occured to me about the end when dent is picking the letters out of the cave man scrabble bag. The question is 'what do you get if you multiply nine by six.' The answer to that is 54. Why does Dent say its 42. 7 times 6 is 42. Any ideas why this mistake was never corrected by the maker of the show and is that mistake in the book as well? Thanks for your time.
the answer to the ultimate question, as deduced by deep thought, is "42". the mice commissioned the earth from the magritheans as a super bio-computer to find out the question. the vogons destroyed the earth before the program had completed, but more importantly the program had already been corrupted by the arrival of the golgafrinchan haidressers, telephone sanitisers, etc. in theory there should have been a vestige of the program left in arthur's brain (as the last earthman), this is what he & ford were trying to expose with the random scrabble letters. the fact that the program was corrupted meant that the question was wrong (ie six by nine).
or.... something like that!
Marvin had of course read Arthur's brain to find the ultimate question, as it was assumed that Arthur, being a last generation product of the Earth, would have the answer in his brain, but no one was interested enough to ask Marvin what the question was. So, as described, due to the corruption of the program, the question that Marvin read in Arthur's brain might have been the ultimate question, but probably wasn't.