is an showing the equivalence of two , or , with different numerators and denominators.
The first and last numbers in the proportion are called the extremes
, while the other two numbers are called the means
In a proportion, the product of the
is equal to the product of the
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
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
One-third is proportional to two-sixths and four-twelfths.
The concept of proportionality is also useful in geometric concepts such as the or when determining if two figures are .
These two rectangles are proportional, or similar, because the ratio between their corresponding measures is constant. Some geometric figures, such as , , , and cubes are always proportional to each other in size.