Ratios Lesson for Kids: Definition & Examples

Instructor: Kadoria Burgess

I have a Bachelor's degree in Elementary Education and Spanish. I have taught for 5 years in bilingual classrooms of various elementary grade levels.

Just as the English language uses words such as 'taller' or 'nicer' to compare one thing to another, math also has a way to compare different things by using ratios. In this lesson, we will learn what a ratio is, what it looks like and how it helps us with many things that we do.

What is a Ratio?

You're having a party, and what party is complete without cupcakes? You decide that you're going to make your own. You've invited five friends to the party, so you have to make five cupcakes. The recipe for five cupcakes calls for 2 cups of flour and 1 cup of milk. To remember this better, your mom suggests that you use a ratio, but what is a ratio?

A ratio compares one thing to another thing. The ratio for your recipe will compare flour to milk. For every 2 cups of flour that you will use, you will need to use 1 cup of milk. There are several different ways that you can show this ratio. It can be written with a colon or 2:1, with the word to or 2 to 1, or as a fraction 2/1.

Ratios4

Scaling Up and Down

The word spread about your party and, all of a sudden, 20 friends want to come to your party. Oh no! You're going to have to make a lot more cupcakes, but your recipe only showed you how to make five. No fear! Scaling up is here! Scaling up means taking your original ratio and multiplying by the same number to show more.

Remember that our original ratio for making 5 cupcakes was 2:1. You know that in order to go from 5 to 20, you have to multiply by four. So, you will multiply both of the numbers in your ratio, the 2 and the 1, by 4. Now, for every 8 cups of flour, you will need 4 cups of milk.

Scaling Up
scaling up

The day before your party, ten friends decide to cancel. Bummer! On top of that, now you have to scale down the ratio for your recipe to only ten cupcakes, but how do you scale down? Scaling down means taking a larger ratio and dividing by the same number to show less.

So, you now only have to make half of the 20 cupcakes. To figure out this ratio, you will take the larger ratio of 8 to 4, and you will divide both numbers by 2, since 20 divided by two is 10. Now, in order to make 10 cupcakes, you will need 4 cups of flour for every 2 cups of milk.

cupcakes scaled up and down

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