Lesson 7.4 Ratios, Rates, and Percents

# Introduction to Percents

#### Materials

• CCB Mathematics pages 230 - 235

#### Standards

• MP.3

• Understand ratio concepts and use ratio reasoning to solve problems.

#### Objectives

• Understand and write percents

• Change fractions to decimals and decimals to fractions

• Change fractions to percents and percents to fractions

• Change decimals to percents and percents to decimals

#### Key Concept

• Percents, like decimals and fractions, represent part of a whole.

#### Vocabulary

Tier 2 Percentsimilarity repeating decimal

## Before Lesson

In this lesson, students learn what a percent represents. They also learn how to write fractions and decimals as percents. To determine their readiness for the lesson, have students solve simple division problems using whole numbers and decimals.

## Background

Tell students that a percent is a ratio that compares a number to 100. The symbol for percent is %. 10% Represents 1/10 as a fraction, and 0.1 as a decimal. Say: Suppose 100 people took a survey on exercise habits. If 10 of the 100 people stated they exercised three times each week, then 10%, 10/100, or 0.1 of the people surveyed exercised three times each week.

## Guided Practice

• Understand Percents
• Compare and Contrast
• Percents as Decimals

## Core Skill

Construct Viable Arguments: Have students read the text. Then organize students into small groups and have them work together to discuss Ginger’s reasoning. Let students work together to determine the correct tip. Since students have not yet learned to find percents of a number, they might use fractions or decimals. One possible solution is using the fact 15%=10%+5%. 10% equals 1/10, so to find 10% of the bill, calculate 1/10 of 30 = \$3. Since 5% is half of 10%, 5% of the bill must be half of \$3, or \$1.50. So the total tip should be \$3+\$1.50=\$4.50.

## Extension

Answer Questions: Ask students: What do percents, fractions, and decimals have in common? Which do you find easiest to work with? Why?

Categorize Everyday Examples: Have students find examples of real-world situations in which fractions, decimals, or percents are used. Encourage students to look in newspapers and magazines, and also to think of jobs or daily events in which they are used. Then have students create a categorization system for the examples. Ask students to categorize the examples and explain the system.