A proportion is a comparison between two ratios that are equal to each other. You will normally use proportions to solve for a single unknown between the two ratios. Remember, a ratio compares two values in a single fraction, whereas a proportion compares two ratios.
Use cross-multiplication to solve proportion problems. Writing out the ratio in words when setting up the equation will help you get the correct answer. Always be careful not to mix up your numerators and denominators. Be sure to understand the difference between ratios and proportions and when to use each of them. Most proportion exercises you’ll encounter will come in the form of story problems, so be sure to double-check how you set up the ratios. Make sure they are set up with the unknown in the proper position.