[hypertele-Xii]

> If we say to someone '99 hundred', they'd immediately understand it as 9,900.

That's definitely untrue. In my native language we never mix tens and hundreds, and it always takes me a moment to parse that "thirteen hundred" means one thousand and three hundred.

[silisili]

Ah, I should have specified in the US. It's more common to say numbers between 100 and 10k as hundreds, unless it's exactly on a thousand. I think most people would say nineteen hundred, or 21 hundred for 1900 and 2100, but nobody would say 20 hundred for 2000(except for military time).