Stepping aside from this heavy discussion to a lighter moment ;) ... I guess an interview question like "How do you divide by 2 without using the divide function?" is probably not intended to test your knowledge but to test other desirable skills/qualities, and the way you answer it would tell something about your personality. Perhaps there is a wittier answer to it than the obvious "multiply by half" or the dull "not possible".
Reminds me of this incident ... my brother was once asked this question towards the end of an interview for a programmer job,
Q.: What is the probability of picking a red ball from a bag containing equal number of red and blue balls?
A.: 0.5
Q: Ok. How would you increase the probability of picking a red ball from the bag?"
Without going into the theory of probability to explain that there wasn't a fair way to do so, he just replied jokingly, "Paint one of the blue balls red".