# The Craft of Word Problems

## CONTENTS OF CURRICULUM UNIT 04.05.01

- Narrative
- Place Value
- Addition and Subtraction (within 10)
- Fact Families
- Addition and Subtraction (within 20)
- Addition and Subtraction with and without regrouping
- Strategies for solving problems
- Lesson 1
- Lesson 2
- Lesson 3
- Lesson 4
- Lesson 5
- Lesson 6
- In the Future
- Mathematics Standards
- Bibliography for Teachers and Students

### Unit Guide

## The Relationship between Addition and Subtraction in Problem Solving

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## Lesson 6

Students have seen the relationship between addition and subtraction using single-digit numbers and two-digit numbers. This last lesson will again practice two-digit word problems. In my four years as a second grade teacher, I have noticed that working with two-digit numbers is an area of weakness for many students, whether they are adding or subtracting.

Discuss how these problems differ from the previous lessons. Discuss how the problems relate to each other. Discuss two-digit fact families. Focus on regrouping in addition and subtraction.

Objective

To have students use the four basic strategies to solve a set of word problems.

To have students communicate the relationship of the problems.

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Problem 1
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60 oranges were in a basket. 25 were sold. How many oranges were not sold?

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Problem 2
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If 25 oranges were sold yesterday and 35 oranges were sold today. How many oranges were sold on both days together?

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Problem 3
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There were 60 oranges. If 35 are still in the basket, how many were sold?

As always, I think it is important to discuss how these problems are similar and different. This discussion will give teachers the opportunity to hear mathematical communication. By now students should be using key terms and vocabulary in their explanations. Students should notice that in all three of these word problems there is regrouping and that this is a fact family. A few students may notice that this lesson only has three problems while all the other lessons had four problems.

This is a great time to give students an opportunity to write a word problem for this set. When students are constructing their own sets of problems, I think it is important to give them the opportunity to work with a partner. Students may even want to create their own set of problems, similar to this lesson. Teachers may want to use one class period to write and construct the problems and another class period to solve them. Students can switch problems with a partner, solve them, discuss them, and give feedback.