Proportion

Using proportion is a very important skill. A proportion is two EQUAL ratios. The fact that they are equal allows you to set up an equation that can be solved.

Here is a sample proportion:

This proportion is not very interesting, because it is already completely SOLVED! The power of proportions comes when you are looking for one of the missing values.

Suppose a question results in the following proportion:

You should already know that the x in the above equation is 6 (look at the top of this page to see!) but let's examine how to solve this proportion.

To solve a proportion, most people use a skill called cross-multiply and divide. This is a two step process:

1. Multiply the two numbers that are diagonally across the equals sign from one another. (2 x 9 = 18)

2. Divide the result of step 1 by the remaining number. (18 ÷ 3 = 6)

Voila! Your answer for x is 6!

What would you like to do now?

• See more examples of cross-multiplying
• Try some cross-multiplying questions
• See some proportion word problem examples
• Try some proportion word problem questions