Welcome to our Math lesson on Definition of Proportion, this is the first lesson of our suite of math lessons covering the topic of Proportion, you can find links to the other lessons within this tutorial and access additional Math learning resources below this lesson.
If two quantities involved in a situation (we call them variables) are related in such a way that if one quantity changes, the other quantity changes at the same (or opposite) degree, we say that these quantities are in proportion with (or proportional to) each other. In simpler words, a proportion indicates to us how one thing changes in relation to another.
For example, if a car travels 240 km with 8L of gasoline, it can travel other for other 720 km with 24 L of gasoline if moving at the same rate (speed). The unit rate u.r. of gasoline consumption therefore is
Since there two unit rates are equal, we say they are in proportion. Hence, it is clear that a proportion includes two equal fractions, i.e. if
then a and c are proportional (as well as b and d).
In other words, if a/b and c/d are two equal ratios or rates, they are in proportion.
We can also write the above proportion in the form
where a is the first term, b is the second term, c is the third term and d is the fourth term of the proportion. The terms a and d are called outer terms or extremes, while b and c are called inner terms or means of the proportion.
Which of the following pairs of fractions are in proportion?
First, we express each fraction in the simplest terms. In a certain sense, a fraction expressed in the simplest terms is similar to the unit rate (in fact, one of the two associated unit rates) we discussed earlier. Thus,
and3/15 = 3 ÷ 3/15 ÷ 3 = 1/5
and12/4 = 3/1 = 3
and9/15 = 9 ÷ 3/15 ÷ 3 = 3/5
|Tutorial ID||Math Tutorial Title||Tutorial||Video|
|Lesson ID||Math Lesson Title||Lesson||Video|
|4.3.1||Definition of Proportion|
|4.3.3||Graph of Direct Proportion|
|4.3.4||Cross Product in Direct Proportion|
|4.3.5||Inverse (Indirect) Proportion|
|4.3.6||Graph of Inverse Proportion|
Enjoy the "Definition of Proportion" math lesson? People who liked the "Proportion lesson found the following resources useful:
We hope you found this Math tutorial "Proportion" useful. If you did it would be great if you could spare the time to rate this math tutorial (simply click on the number of stars that match your assessment of this math learning aide) and/or share on social media, this helps us identify popular tutorials and calculators and expand our free learning resources to support our users around the world have free access to expand their knowledge of math and other disciplines.