So I went to a hardware store for some weather-stripping because my door isn't the same shape as its frame and "having it closed" was basically the same as "having it open." I went to the register to pay for my stuff.
The cashier told me my total was $7.26 so I gave her a $20 bill. After she had asked me for my phone number for some reason, I realized I had exact change.
I might as well have told a dog to read me the newspaper. She told me she had already hit the "$20 button" on the register. We had passed the point of no return.
So now there were two stacks of money on the counter: my $7.26 to pay for my $7.26 purchase, and the change the computer had told her to give me from my $20. I wasn't really annoyed at this point, because I still had a thorough grasp of my lack of proficiency with anything involving numbers. I'm totally freakin' awesometaculariffic with words, but as soon as you put numbers in anything, my brain just shuts off. So I believe that most anyone can grasp any mathematical concept that I can, so maybe she just didn't understand what I was saying.
Figuring this was the kind of arithmetic they prime kindergarteners on, I asked again. I would also like to point out that this was a white, American, English-speaking lady. So there are no cultural or language barriers to work around, which is a shame because that would be completely excusable. But still annoying.
She looked at the exact change from my pocket sitting next to the change that she had given me from the twenty dollar bill and told me there was $15 on the counter.
How do you not understand that the exact change for the price of the thing PLUS the $12.74 change you just gave me equals $20?! So I separated the money out so it was easier to look at. Instead of two random-looking piles of cash, we now had this.
Surely anything that stands on two legs and has a pulse can see that this money on the counter adds up to twenty dollars, and as a cashier you might rather have small bills and change in your drawer than a $20 bill that you can't do anything with.
I finally decided that the time I'd stood there trying to explain basic addition to an adult was not worth the convenience of having one piece of paper that I am statistically less likely to spend than the now four basically monetary worthless pieces of paper and ten annoying jangly pieces of metal that I honestly sometimes just throw away. I left the store more confused than the cashier was, but surely for different reasons. How did I, of all people, out-math someone? I looked for plagues of locusts or doom-bringing horsemen as I drove home. All of which I would somehow defeat with my SUPER MATH POWERS OF INFINITY. TIMES A MILLION.