I was at the bank the other day, making a deposit. I don't usually bother to use the calculator that sits on the counter, but that day I checked my aritmetic using the cheap TI calculator provided. For some reason it was set to three digits after the decimal point. On an addition of two amounts in the thousands of even dollars (no cents), the calculator added 1/10 of a cent.

I just thought that was interesting.

That's really weird. You don't have a model number do you?

I'll try to remember to get it next time I'm at the bank.

I went back to the bank and where there had been two calculators, now there is only one. It was a TI 1795SV. I think they removed the offending one. I couldn't make the remaining one misbehave at all. It had previously come up with 209.33 + 807.67 = 1017.001, but the remaining calculator dropped all cents and I saw no ready way to change the notation. I can't seem to raise any TI pages to find instructions, but I'm guessing that it was just a faulty calculator, or perhaps low batteries.

Could it have been an operator error?

Of course it could have been an operator error, but I was surprised enough at the result to clear the calculator and do it again. I had already done the arithmetic in my head, and was just checking. It was, after all, a simple addition, with a number of cents that happened to come out to even dollars, and both times, it returned $$$$.001. The dollar amounts were correct each time. If there's a way to make that model read out even amounts in 1/10 cent notation I can't find it, so I suspect the calculator misbehaved, and that this explains its disappearance the next day.