Q: Context: Vinegar is a liquid consisting of about 5 -- 20 % acetic acid (CH COOH), water, and other trace chemicals, which may include flavorings. The acetic acid is produced by the fermentation of ethanol by acetic acid bacteria. Vinegar is now mainly used as a cooking ingredient, or in pickling. As the most easily manufactured mild acid, it has historically had a great variety of industrial, medical, and domestic uses, some of which (such as its use as a general household cleaner) are still commonly practiced today.

Question: what is the percentage of acetic acid in vinegar?
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The relevant sentence in the passage is: Vinegar is a liquid consisting of about 5 -- 20 % acetic acid (CH COOH), water, and other trace chemicals, which may include flavorings. So the answer is 5 -- 20 %.