Look, just because you don't want to do the math doesn't mean I want to do it either. You asked me to pick up X at the store and I did, but if you didn't pay attention to the receipt then it shouldn't be my job to calculate the taxes. ("Oh, but you have a calculator and I don't.") And you expect me to drop whatever I'm in the middle of just to pick up a calculator?
Argh! It's all the inconsiderate acts, but mostly the small ones since they're the most common, of my sister that irk me the most. Just because we're blood related doesn't mean I owe you anything. I wouldn't protect child, sibling, parent, or spouse from justice. Seriously.
I've found myself getting easily annoyed by a lot of little things lately. Just ask andrewshead, I ranted half of yesterday morning at every little thing that seemed wrong. Arbitrary password character restrictions, public knowledge or time-sensitive security questions, among other things.