up the other questions into smaller banks would allow you to spread your 2-3 required questions throughout the quiz, but they would be in fixed locations, not random.
note that's just an example. there are lots of ways you could rearrange it.
splitting the questions into smaller banks does change the probability of picking any one of them slightly. with 81 questions in the non-required pool, each has a change of 47/81 = 0.580247 chance of being picked. if you pool them into 24 out of 41 and 23 out of 40, then those in the first group have a 24/41 = 0.585366 chance of being picked and those from the second 