What is ratio and proportion?

Answer 1

A ratio, similar to a proportion, is the value of one number or measurement in relation to another, and is often symbolized as x:y, x/y, or "x to y." Conceptually, ratios can be thought of as fractions and are often simplified the same way. For instance, if a cocktail recipe calls for 2 oz. of liquor for every 4 oz. of juice, the ratio of liquor to juice is 2:4, 2/4, or "2 to 4." However, 2:4 will almost always be simplified, in a similar way that fractions are, and written as 1:2. The main difference between the simplification methods of ratios vs. fractions is that for fractions, a value such as 10/6 will often be reduced to 1 2/3, whereas ratios will never pull an integer out of a fraction like that. In this particular case, the ratio would be 5:3, 5/3, or "5 to 3," not 1 2/3:3.

The subtle, but meaningful difference in the usage of the terms proportion and ratio is that proportions often imply the combined totality of the two values or measurements you're relating as opposed to ratios, which are used to describe the values' relative independence. For example, you would say, "equal proportions," "directly proportional," and "inversely proportional," but you wouldn't say, "equal ratios," "directly rational," or "inversely rational."