TITLE: Does 17% have to be equal to 0.17?
QUESTION [15 upvotes]: I have a friend who believes that 17% doesn't have to be equal to 0.17.  Even though he says that 17% is equal to 0.17 on its own, he says that 17% at any other time is not equal to 0.17, referring to the argument that $17\%x \neq 0.17$. No matter how I try to explain it to him, he won't believe me when I say that 17% is always equal to 0.17, no matter what. Does anyone have a good explanation for this?

REPLY [2 votes]: This question almost seems like it should be on English SE rather than Math. There is a failure to understand the English language more than there is a failure to understand the math; it seems everyone agrees on the numbers, it’s the words that are giving trouble.
"17% of something" means, in the English language, "17% multiplied by something," so yes, you can still replace 17% by 0.17: the statement just becomes "0.17 multiplied by something" and is still completely true.