How to Write Proportions

Understanding proportions is an important concept in daily life and in the workplace. Proportions are two statements that are equal to each other, although they may have different variables that do not appear to be equal at first glance. Money offers proportion issues, for instance. One dollar is the same as four quarters, 10 dimes, 20 nickels or 100 pennies. Setting up a proportion formula for this is easy, but learning how proportions work can be a challenge for those who are new to the topic.

Things You'll Need

• Pencil
• Paper

Instructions

1. Write the proportion "18:6 = 3:1." This is read as "18 is to 6 as 3 is to 1."

2. Write the proportion "18/6 = 3/1." This is the same as 18:3 = 3:1. It is also read as "18 is to 6 as 3 is to 1."

3. Cross multiply. Multiply the numerator of one part of the formula by the denominator of the other. in this example, you would create the formula "18 x 1 = 3 x 6." This reduces to 18 = 18, which is correct. The proportions are equal.

4. Solve for a missing variable in a proportion by cross multiplying. As in the above example, imagine the 6 is missing. We would write "18/X = 3/1." This would become 18 x 1 = 3 x X, which is 18 = 3x. Divide both sides by 3 to solve for X, and you get X = 6.

5. Plug 6 into the equation 18 x 1 = 3 x X and you get 18 = 18.

Tips & Warnings

• If you get confused, just start the proportion computation from the beginning.