If 20 minutes was used because it's round, then we would expect 40 minutes to be used commonly. I'd say 45 minutes is used much more often. As for non-time-rel

If 20 minutes was used because it's round, then we would expect 40 minutes to be used commonly. I'd say 45 minutes is used much more often. As for non-time-related units, I hear 25 deko more often than 20 deko when buying food. I don't think there's really a distinction between building up and down. When you're talking about 250 meters do you build up from meters or down from kilometers? I think both.