I gotta ask myself, "Uh?....nevermind."
I was at my local drugstore where Christmas items were marked "75% off."
Now, although I can calculate the price of a marked down box of ornaments in my head, I don't get upset if someone wants to use a calculator.
HOWEVER, rather than simply multiplying each item by .25 to get the price, she multiplied each item by .75, got an answer, and then subtracted it from the original price.
I was in line a long time that day, because she did that with everyone who was buying sale items. LOL!