Do not ever be rude or condescending to someone who asks "obvious" questions, no matter how obvious or silly you think the question is.
For one, in some cultures asking an obvious question is just a polite way of acknowledging the situation. So for example, if you just put your jacket on and start clocking out, a co-worker asking "oh, you done for the day and heading out now?" doesn't deserve you sneering at them like an idiot, scoffing, and saying "uh duh, just like I do every day at this time" when it's likely they knew the answer, but were just asking as a polite way of acknowledging the situation.
But even if they were genuinely unsure that you're leaving even though it seems obvious to you from context clues, so what? What does being rude and condescending to them achieve? Maybe they couldn't sleep last night so they're really out of it today, maybe they're dissociating, maybe they're about to pass out from low blood sugar, maybe some other employees sometimes put on their jacket and only clock out briefly but come back.
There's all sorts of reasons they could be confused about whether or not you're leaving, but intentionally making them feel bad achieves nothing except, well, making them feel bad. Either way, they're not hurting you or anyone by asking a "stupid" question, so there's no point in being rude about it. If you still want to make them feel bad about themselves for looking "stupid" when they weren't hurting anyone, that is the mindset of bullies and abusers.
Thank you everyone who is pointing out in the notes that this is usually an attempt to connect with someone and/or strike up a conversation. Because honestly in my experience 9 times out of 10 when someone asks an "obvious" question that's what they're trying to do. If someone walks into the kitchen and asks "oh are you cooking?" while you're standing over the stove holding a spatula, they probably already know the answer, but they're just trying to start a conversation with you and connect to you.
All the more reason it's sad and hurtful when these attempts are met with sneering and being treated like an idiot.
