Something I've always wondered about was the usage of "maths" in the British Isles. (Not sure of the exact geography.) For example, from Elementary, Moriarty has a line where she says, "You've done the maths," in reference to her daughter and that she cannot be Sherlock's.
The usage seems quite common, but it's not usual for folks in the United States. We would probably say, "You've done the arithmetic."
What's the question? Your observation is correct; that is the term used over here.
