Why 42, you ask? Well, that's what the computer said, and as we all know, computers are always right. Of course the computer also said that we really never knew what the question was in the first place. As descendents of the Golgafrinchans, we all should feel a small amount of guilt that we beat out the prehistoric apes who were supposed to evolve into the components of the new supercomputer that was to calculate the correct question, so it's all moot anyway.

In an effort to get some insight into what the true question is, Arthur Dent (who was unaware at the time of his Golgafrinchan lineage) randomly drew Scrabble tiles to come up with "WHAT DO YOU GET IF YOU MULTIPLY SIX BY NINE". Naturally, this question is irrational but completely understandable considering the source. So there you have it.