A
proportion is an showing the equivalence of two , or , with different and .
ba=dcora:b=c:d
The first and last numbers in the proportion are called the
extremes, while the other two numbers are called the
means.
ad↓means:↑b=↑c:extremesd↓
In a proportion, by the , the product of the extremes is equal to the product of the means.
As an example of
proportionality, consider slices of pizza. Depending on the number of times it has been sliced, the same amount of pizza could be cut into
1, 2, or
4 pieces.
In this case, one-third of a pizza is the same amount of pizza as two-sixths or four-twelfths. If the simplified forms of two fractions are equal, then they are said to be
proportional. For example, one-third is proportional to two-sixths and four-twelfths.
Note that proportions are often used in geometric concepts such as the or when determining if two figures are .