I'd say it was out of place. Professors are allowed to goof around sometimes and entertain simply because they're in a higher place of power than you. Often times the professors goof around to make the class laugh and to get on their good side. If a student does it, however, it only looks like he or she is trying to be a smart ass or a showoff in most cases. 10 points off isn't that bad...there's no telling what would happen if someone did that in my classes.
-Lasereth