A proportion is a statement that two ratios are equal. Proportions can be written as equivalent fractions or as equal ratios.


Equivalent fraction :  =
Equal ratio :  1:2 = 7:14

terms of a proportion

There are four terms of a proportion, often written as:
or a:b = c:d
The terms in the proportion are a, b, c, and d. The extremes are a and d, and the means are b and c. The product of the means and the product of the extremes are equal.
1:2 = 7:14
Note that 2 × 7 = 1 × 14, showing that the two ratios are proportional.

Related word proportional.

See also equal ratios, scale.