Are these formS correct? The first is fine, except for the fact that we'd probably say 'a hundred' rather than 'one hundred'. We mainly use the numerical 'one' to specify a certain number i.e. one rather than two or three. But as nobody lives to be two or three hundred, there's no need to say 'one'. The second sounds less natural. 'Till', or more correctly 'until', is usually followed by a time expression (e.g. until 5 pm) or a whole phrase ( e.g. until you've finished). We might say "Some people live till they are a hundred years old", though.

Actually, conversationally both of these make sense! Saying " Some people live to be one hundred years old" is slightly more formal than "some people live till one hundred years old." The word "till" is slang and generally you would use "until" in writing.

some people live TILL .... :)