# What is a ratio?

## What Does Proportion Mean

We explain what a proportion is and some examples of this equal relationship. Also, the types of proportionality that exist.

## What is a ratio?

In mathematics , the relationship of equality that exists between two ratios , that is, between two comparisons between two determined quantities , is known as a proportion . That is: if a / b is a ratio, then the equality a / b = c / d will be a proportion.

For example, if a business selling pizza has a gain of \$ 15,000 and an expense of \$ 5,000, we can say that the company has a ratio of 3. In the same way, if this business will cost \$ 20 prepare two pizzas (20/2 = 10), so making four pizzas would cost \$ 40 (40/4 = 10). If both reasons are expressed in a formula: 20/2 = 40/4. Here is a proportion. The theorization about this type of relationship was elaborated in Greek antiquity , and it is attributed to Eudoxio de Cnidos, teacher of the famous Euclid of Alexandria, thanks to whom the teachings of his teacher survive , collected in the book V of the Elements of Euclid. . Types of proportionality

We can say that a proportion occurs in mathematical situations in which the values of two quantities depend on each other in a direct way (direct proportionality). Thus, when one of the values of the relationship increases, the other will necessarily also increase , as is the relationship between temperature and energy , for example : the higher the temperature, the higher the energy and vice versa. On the other hand, in a relationship in which the increase of one of the terms leads to the decrease of the other, it is said that we are facing an inverse proportionality. This can be expressed as two terms being inversely proportional: when one goes up the other goes down, and vice versa. Such is the relationship between speed and time : the higher the speed, the shorter the time it will take to reach our destination, and vice versa. See also: Trigonometry

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