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# Writing Ratios

Lesson 1 of 3

## Objective: SWBAT understand ratios and what they represent.

*45 minutes*

#### Introduction to Ratios

*15 min*

I will lead the class through a series of exercises that will be used to explain what ratios are. For each exercise, I will ask the class "*What are the two things being compared?*"

1 - I will select 4 boys and 3 girls to stand at the front of the class.

2- I will give each group 7 red blocks and 2 green blocks.

3 - I will ask students who have a dog to stand on one side of the room and students who have a cat to stand on the other side of the room.

I will explain to the class:

*Each situation we saw represented a ratio. How would you define a ratio?*

After hearing from students, I will give them a formal definition of ratio.

**Ratio** - a comparison of two numbers by division

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#### Lesson

*15 min*

This lesson will focus on the various ways that ratios can be written and interpreted. I will lead students through a couple of examples using a Think-Pair-Share strategy. With this strategy students will take a few minutes to individually think about the questions, discuss it with a partner (or group), and then we will discuss it as a class.

**Example 1 **(Writing Ratios - Example 1)

**The coed basketball league has five times as many boys on it as girls. What is the ratio of boys to girls? How can the ratio be written?**

As we discuss the example as class, most students will have reached the comparison of five to one. I will introduce the different ways of writing this ratio.

- We can write ratios using a colon symbol. 5 : 1
- We can write ratios using the word "to" 5 to 1
- We can write ratios using fractional notation. 5/1
- We can write a ratio using words "For every…" For every 5 boys, there is 1 girl.

I will also show students how this ratio can be represented visually through a ratio table and tape diagram. These will be used more in later lessons.

**Example 2**

**What is the ratio of boys to girls in the class? Choose 3 different ways of representing this ratio.**

Students will be given 5 minutes to work on the question independently. Then I will randomly call students to the board to show how they wrote the ratio.

#### Resources

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#### Group Work

*10 min*

To assess students' understanding of writing ratios, they will be given the following group work.

**Group Work**

Describe a situation that represents each ratio below. Think about real life examples!

Example: 1 : 2 Possible ratio relationship. For every 1 grade in the school, there are 2 classes.

1)1 : 12

2)2 : 48

3)5 : 2

4)8: 1

After 10 minutes, I will ask students to share their answers.

**Possible Answers**

1) For every 1 carton there are 12 eggs.

2) For every 2 days there are 48 hours.

3) For ever 5 weekdays there are 2 days in the weekend.

4) For every 8 periods there is 1 day.

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#### Lesson Summary

*5 min*

For the lesson summary, I want students to begin thinking about equivalent ratios. I will pose questions to the class to lead them into a discussion.

*Can ratios be scaled up or down? Can you give an example using one of the ratios from today's lesson?*

Students should discuss that since ratios are fractions, they can be scaled up or down to find equivalent ratios. (Look for *MP3*)

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- UNIT 1: First Week of School
- UNIT 2: Properties of Math
- UNIT 3: Divisibility Rules
- UNIT 4: Factors and Multiples
- UNIT 5: Introduction to Fractions
- UNIT 6: Adding and Subtracting Fractions
- UNIT 7: Multiplying and Dividing Fractions
- UNIT 8: Algorithms and Decimal Operations
- UNIT 9: Multi-Unit Summative Assessments
- UNIT 10: Rational Numbers
- UNIT 11: Equivalent Ratios
- UNIT 12: Unit Rate
- UNIT 13: Fractions, Decimals, and Percents
- UNIT 14: Algebra
- UNIT 15: Geometry