In this publication, we will consider what proportion is, what elements it consists of, and also analyze the main property of proportion along with a practical example.
Definition of proportion
Proportion is the equality of two or more.
Let’s say we have two equal relationships:
If we put an “equals” sign between these ratios, then we get a proportion:
Elements of proportion
- extreme – marked with red circles;
- average – circled in green.
Basic properties of proportion
In any correctly composed proportion, the product of the extreme elements is equal to the product of the middle ones.
Those. a · d = b · c.
To make it easier to remember, the so-called “rule of the cross”, i.e. cross multiplication of lying elements.
Example
Let’s check the main property and the rule on the proportions below:
Both ratios result in the same number (two), so the proportion is correct.
So we can multiply its elements using the “rule of the cross”:
Get:
12 · 15 = 6 · 30 or 180 = 180