Do the math:
There are actually two answers to this question.
First, “maths” looks plural and is preferred by some because “mathematics” is plural. The problem with that is “mathematics” is no more plural than “physics” or any other compound noun. It is a rational sounding utterly incorrect argument. If we said “mathematics are cool” then there might be a case. But we say “mathematics is cool.”
Second, some people say maths and some people say math, and that’s how language works. That is a valid argument, but if you are walking around in the US saying “maths” instead of “math” be aware that you are demonstrating an anglophile affection, which is fine, as long as you know you are doing it. Please remember to demonstrate other anglophile affections such as referring to “English Muffins” and “Crumpets” and telling your friend “I’ll knock you up in the morning” when you merely intend to come by to walk to work together. Most importantly, if you have switched to “maths” from “math” because of some rational argument you once heard, just know there isn’t a rational argument. It is just a matter of usage. It is arbitrary. There is no readon. And if you are in the US you are using the non-standard usage. If you are in England or somewhere fine, talk funny all you want!
The conversation about “knocking up” has developed here, on Facebook and on Twitter. Interestingly a lot of Brits claim this is simply not a thing Brits say, yet it is. It may simply be patchy in its use, but it really is a British saying. More so than an English Muffin being a Crumpet (I know it is not, but I do love the reaction to the comparison among the Crumpet Sympathizers). Anyway, “I’ll Knock You Up” is defined in many places, and used by many Brits, to mean to rouse, wake up, call on, etc. another person. In American English, it means to make pregnant. In at least some forms of British, when does not “get pregnant” but one “fall’s pregnant” and if one chooses one might have the baby in the hospital, in America, or in hospital, in British-English areas.
Anyway, here’s the Google Ngram for various uses of “knocked”: