#18 is kind of interesting, because there's two possible answers. For a modern analogue clock where the hands move in fixed increments, rather than smoothly, th

#18 is kind of interesting, because there's two possible answers. For a modern analogue clock where the hands move in fixed increments, rather than smoothly, the answer is simply 5 minutes. For older ones it's 25/6 minutes. I like #12, just because it begs to be answered with "perfectly".