Ratios are all about comparing two quantities. Think of a recipe for lemonade that calls for 1 cup of lemon juice and 4 cups of water. The relationship between the lemon juice and water is a ratio.

There are three common ways to write a ratio. Let's use our lemonade example, comparing lemon juice to water.

All three forms express the same idea: for every 1 part lemon juice, you need 4 parts water. The order of the numbers is crucial. A ratio of 4:1 would mean 4 cups of lemon juice to 1 cup of water, which would make for some very sour lemonade! The quantity mentioned first always comes first in the ratio.

Because ratios can be written as fractions, you can also express them as decimals or percentages. This is especially useful when you need to compare different ratios.

For example, if one recipe has a lemon-to-water ratio of 1/4 and another has a ratio of 2/5, which one is more lemony? Converting them to decimals can make the comparison easier.

Recipe 1: $1 \div 4 = 0.25$ Recipe 2: $2 \div 5 = 0.40$

The second recipe has a higher value, so it's more concentrated.

You encounter ratios every day, even if you don't notice them. They're a fundamental tool for scaling things up or down and keeping relationships consistent.

• Cooking: Recipes rely on ratios. If you want to make a bigger batch of cookies, you double all the ingredients, keeping the ratios the same.
• Maps: The scale on a map is a ratio. 1:100,000 means 1 inch on the map represents 100,000 inches in the real world.
• Screens: The shape of your TV or phone screen is described by an aspect ratio. A 16:9 aspect ratio means the screen is 16 units wide for every 9 units high.

Understanding ratios helps you make sense of the world, from adjusting a recipe to understanding the technology you use daily.