Author:
Subject:
Ratios and Proportions
Material Type:
Lesson Plan
Level:
Middle School
6
Provider:
Pearson
Tags:
Language:
English
Media Formats:
Text/HTML

# Cooking with Fractions

## Overview

Students determine how many times they would need to fill a quarter cup to measure the ingredients in a recipe.

# Key Concepts

This lesson informally introduces the idea of dividing by a fraction. Students must figure out how many times a quarter cup must be filled to measure the ingredients in a recipe. This involves dividing each amount by $\frac{1}{4}$. Here are some methods students might use:

• Add $\frac{1}{4}$ repeatedly until the sum is the desired amount. Count the number of $\frac{1}{4}$s that were added.
• Start with the amount in the recipe. Subtract $\frac{1}{4}$ repeatedly until the difference is 0. Count the $\frac{1}{4}$s that were subtracted.
• Draw a model (e.g., a bar or a number line model) to represent the amount in the recipe. Divide it into fourths and count the number of fourths.

# Goals and Learning Objectives

• Learn how to divide by a fraction.

# Lesson Guide

Have students discuss with their partner whether Denzel can make the recipe using only his $\frac{1}{4}$-cup measuring cup.

# Mathematics

Before students begin the Work Time problems, be sure they see that Denzel can make the recipe—he just needs to fill his measuring cup several times for each ingredient.

ELL: When working with ELLs, it is important to link new concepts to students’ prior knowledge and experiences. This allows students to make more meaningful connections with the new mathematical concepts they are learning.

## Opening

Here is the list of ingredients for a recipe Denzel wants to make.

1 cup chopped almonds
1$\frac{1}{2}$ cups dried apricots
1$\frac{1}{4}$ cups water
$\frac{1}{2}$ cup honey
2$\frac{1}{2}$ cups flour
2 tablespoons butter
2 teaspoons baking powder
1 egg
1 teaspoon vanilla
1 teaspoon salt

As Denzel is about to measure out the ingredients, he realizes that the only size measuring cup he has is a $\frac{1}{4}$-cup measuring cup. The first five ingredients are given in cups.

Discuss:

• Can Denzel measure the first five ingredients using only his $\frac{1}{4}$-cup measuring cup?

# Lesson Guide

Discuss the Math Mission. Students will explore how to measure the ingredients for a recipe using only a
$\frac{1}{4}$-cup measuring cup.

## Opening

Explore how to measure the ingredients for a recipe using only a $\frac{1}{4}$-cup measuring cup.

# Lesson Guide

Have students work in pairs. Be sure students understand what to do. For each of the first five ingredients, they need to enter the number of times Denzel will have to fill the $\frac{1}{4}$-cup measuring cup.

ELL: Model or demonstrate the activity step by step. This modeling will ensure that ELL students understand the task and therefore focus on the mathematics of the activity rather than on trying to figure out the directions. (To check for understanding, have students retell the steps of the task to a partner.)

SWD: Decide how you will partner students together for this task. Partnering students by skill level will allow for more efficient provision of teacher support, while partnering students heterogeneously will promote cooperative teaching and learning opportunities for students with varying mathematical skills. Monitor partnerships to ensure all students’ progress. It is often best practice to have students with disabilities be partners with typically developing peers.

# Interventions

Student has difficulty getting started.

• What do you know?
• What are you trying to find?

Student is not working systematically.

• How can you organize your work to keep track of how many $\frac{1}{4}$-cups you are combining (or subtracting)?
• Can you draw a diagram?

Student is making guesses rather than using reasoning.

• Will your answer for 1$\frac{1}{2}$ cups be more or less than your answer for 1 cup?

# Mathematical Practices

## Mathematical Practice 7: Look for and make use of structure.

Students may use the fact that 2$\frac{1}{2}$ cups is 1 cup + 1 cup + $\frac{1}{2}$ cup and use their earlier answers to reason that Denzel would have to fill the $\frac{1}{4}$-cup measuring cup 4 + 4 + 2 (or 10) times to measure the flour. Be sure to discuss this practice in Ways of Thinking.

• Rewritten recipes will vary in format, but should include the following information:

1 cup chopped almonds: Fill the $\frac{1}{4}$-cup 4 times.

1$\frac{1}{2}$ cups dried apricots: Fill the $\frac{1}{4}$-cup 6 times.

1$\frac{1}{4}$ cups water: Fill the $\frac{1}{4}$-cup 5 times.

$\frac{1}{2}$ cup honey: Fill the $\frac{1}{4}$-cup 2 times.

2$\frac{1}{2}$ cups flour: Fill the $\frac{1}{4}$-cup 10 times.

• Discussions will vary.

# How Much of Each Ingredient?

Determine how many times Denzel needs to fill his $\frac{1}{4}$-cup measuring cup to get the right amount of each of the first five ingredients.

• Rewrite the recipe so that it shows how many $\frac{1}{4}$-cups are needed of each of the ingredients.
• 1 cup chopped almonds = [   ] $\frac{1}{4}$-cups
• 1$\frac{1}{2}$ cups dried apricots = [   ] $\frac{1}{4}$-cups
• 1$\frac{1}{4}$ cups water = [   ] $\frac{1}{4}$-cups
• $\frac{1}{2}$ cup honey = [   ] $\frac{1}{4}$-cups
• 2$\frac{1}{2}$ cups flour = [   ] $\frac{1}{4}$-cups

Try making a diagram to represent the amount of each ingredient. How many 1/4 -cups does your diagram represent?

# Preparing for Ways of Thinking

Look for student pairs using different methods for determining how many times Denzel will have to fill the $\frac{1}{4}$-cup measuring cup. Choose a variety of strategies to present during Ways of Thinking.

Some possible strategies to highlight:

• Add $\frac{1}{4}$ repeatedly until the sum is the desired amount. Count the number of fourths that were added.
• Start with the amount in the recipe. Subtract $\frac{1}{4}$ repeatedly until the difference is 0. Count the fourths that were subtracted.
• Draw a model (e.g., a bar or a number line model) to represent the amount in the recipe. Divide it into fourths and count the number of fourths.

Select students who solved the Challenge Problem to present during Ways of Thinking.

Presentations will vary.

# Challenge Problem

• $\frac{1}{4}$ cup honey; 1$\frac{1}{4}$ cups flour

# Prepare a Presentation

• Describe the strategy you used to rewrite the recipe so that it could be followed using only a $\frac{1}{4}$-cup measuring cup.

# Challenge Problem

Suppose that Denzel decides to make only half of the recipe.

Remember the recipe called for:

• $\frac{1}{2}$ cup of honey
• 2$\frac{1}{2}$ cups of flour

How much honey will he need? How much flour?

Think about what you did to solve the problem. Did you use the same approach for each ingredient?

# Lesson Guide

Have students present the various strategies they used. Discuss these strategies as a class.

# Mathematics

Students who solved the Challenge Problem should share their solutions and methods. Some students might recognize that the problem requires finding $\frac{1}{2}$ of a given amount and recall that “of” means “times.” So, for the flour: $\frac{1}{2}$ of 2$\frac{1}{2}$ cups = $\frac{1}{2}$⋅2$\frac{1}{2}$ c = $\frac{5}{4}$ c = 1$\frac{1}{4}$ c. Other students might use less formal methods, such as drawing a diagram.

# Ways of Thinking: Make Connections

Take notes about your classmates’ strategies for converting the quantities in the recipe.

• Can you explain why your strategy makes sense?
• Where can I see the total amount of the ingredient in your model?
• Where can I see the 1 4 -cups in your model?
• How are your representations for the different ingredients alike? How are they different?
• How is your strategy similar to other strategies that your classmates presented? How is it different?