Ever notice how when someone says that something will take ten minutes, you interpret this as "it will take approximately ten minutes," but when they say it will take one hour, twelve minutes, and nine seconds, you interpret this as "it will take exactly one hour, twelve minutes, and nine seconds?" I wonder why this is. Maybe it's conditioning—someone started doing it, and then more people started doing it, and then it became a part of our culture like "you're fired." Or, maybe it's because those numbers are easier to say or understand because they take less time to say. If you're going to go to the effort of saying such a long value, it must be correct; if you spend less time saying it, then it was probably just an estimate. That would explain why we'd choose 2:00:00 over 1:48:17, but not why we'd choose 5:00 over 7:00. For numbers between 0 and 100, what's the appeal of 25 over 30? Is 25 really "simpler," perhaps because it's 100/4, whereas 30 is 3*100/10? Are we really going through all of that when we say that something is 25% done instead of 30% done, or is it just that we internally think of it as a fraction, and then convert that to a percentage?