Adding and Subtracting 10

Introduction

In this lesson plan, we will explore the concept of adding and subtracting 10 with multiples of ten. Various activities, including arranging mixed-up sequences and using different representations such as bundles of ten straws, towers of ten cubes, and ten-cent coins, will reinforce their understanding. By the end of the lesson, your learner will be able to identify ten more or ten less than any given multiple of ten, preparing them for solving equations that involve adding and subtracting ten.

Before beginning the lesson, your learner should be able to count and write multiples of ten.

Key Concepts for Adding and Subtracting 10

Here are a few concepts that are helpful to know for the lesson:

• Patterns in Multiples of Ten: Multiples of ten always end in 0. The first digit of each multiple of ten follows the counting sequence (e.g., 10, 20, 30, etc.). Recognizing these patterns helps in identifying the previous and next multiple of ten.
• Exploring Ten More and Ten Less: Building on the concept of one more and one less, we extend this to finding ten more and ten less. Finding ten more involves moving to the next multiple of ten, and finding ten less involves moving to the previous multiple of ten.
• Using Patterns to Add and Subtract Ten: Using the patterns in multiples of ten and identifying ten more and ten less, we can quickly add or subtract ten from a given multiple of ten. For example, adding ten to thirty (3 tens) results in forty (4 tens), and subtracting ten from forty results in thirty.

Teaching Plan

The following activities will help your learner become confident with adding and subtracting 10 with multiples of ten.

Examples and visuals to support the lesson:

1. Exploring Patterns in Multiples of Ten

Begin by using towers of ten cubes to explore ten more and ten less.

• Place towers side-by-side increasing multiples of ten and ask your learner to look for and describe patterns in the sequence of numbers.
• Guide your learner in recognizing that the numbers are increasing and decreasing by the same amount each time. Move forward then backward through the sequence.

Ask your learner questions to draw attention to the difference of ten between consecutive multiples of ten.

• Initially use tens language to describe the quantities. For example: "This is one ten; how many more do we need to make two tens? This is four tens; how many fewer to make three tens?"
• Then progress to using the proper number names. For example: "This is ten; how many more do we need to make twenty? This is forty; how many fewer to make thirty?"
• Then mix up the sequence of the towers and challenge your learner to arrange them in increasing or decreasing order. Emphasize the pattern of ten more or ten less as you move through the sequence.

Skill Check
I can use cube towers to find multiples of ten more and ten less than a number.

2. Understanding Ten More and Ten Less

• When your learner is confident moving through the sequence of multiples of ten, choose any multiple of ten and ask how many more/fewer is needed to make the next/previous multiple of ten.
• Use a variety of representations such as bundles of ten straws, ten frames, ten-cent coins, etc.
• Repeatedly add and then remove an additional ten while using the following stem sentence: "This is ___. Ten more/less than ___ is ___."
• Once your learner has had plenty of experience using resources where the tens can be physically manipulated, progress to abstract models such as a number line or Gattegno chart.
• Just as before, ask your learner to identify ten more and ten less than a given multiple of ten. The goal is for your learner to be able to identify ten more or ten less than a multiple of ten without using objects or visual aids.
• You can use missing number problems for ongoing practice.

Skill Check
I can find ten more and ten less than a multiple of ten without counting.

3. Adding and Subtracting Ten

• Next, have your learner practice solving equations that involve adding and subtracting 10 with multiples of ten.
• To prepare your learner for reading and writing equations, progress to using the vocabulary words "plus" and "minus." Make sure that your learner understands that "plus ten" refers to ten more and that "minus ten" refers to ten less.
• Start with physical objects or pictures to reinforce your learner's understanding of plus and minus.
• Demonstrate how the connection between plus ten and minus ten can be represented using diagrams or function machines.
• Finally, provide a variety of missing number equations for your learner to practice adding and subtracting 10.

Skill Check
I can use what I know about ten more and ten less to add and subtract 10.

Summary

By the end of this lesson plan, your learner will have developed a strong understanding of the concept of adding and subtracting ten with multiples of ten. They will have practiced using physical objects and abstract models like number lines and Gattegno charts to reinforce this knowledge. Through engaging activities and repeated practice, learners will be able to confidently identify ten more or ten less than a given number and solve equations involving adding and subtracting ten.

Teaching Plan adapted from NCETM under OGL license v3.