 "A" and "D" are called its "extremes", and "B" and "C" are called its "means".The equality of three or more ratios, like "A"∶"B" = "C"∶"D" = "E"∶"F", is called a continued proportion.Ratios are sometimes used with three or even more terms, e.g., the proportion for the edge lengths of a "two by four" that is ten inches long is therefore

a good concrete mix (in volume units) is sometimes quoted as

For a (rather dry) mixture of 4/1 parts in volume of cement to water, it could be said that the ratio of cement to water is 4∶1, that there is 4 times as much cement as water, or that there is a quarter (1/4) as much water as cement.