[recursive]

Even "ten times more" isn't exactly clear in my opinion. 100% more is two times. 900% more is ten times. Ten times more is... eleven times?

I try to say "{x} is ten times {y}", which is, as far as I can tell is unambiguous. (Mostly, what's ten times colder?)

[telotortium]

"x more than y" means "y + x" - a sum. "x% more than y" means "y + x% = y + y×(x÷100)" and "x% less than y" means "y - x% = y - y×(x÷100)".

To me, "x times more than y" means the same as "x times as much as y" only "y×x" and "x times less than y" means "y÷x". I guess this might seem ambiguous if you bracket the expression like "x times (more than) y", but in practice it's bracketed like "x (times more than) y".

(Native American English speaker)