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## General

Students learn to add to 100 crossing ten with addends less than 10.

2.NBT.B.5
2.OA.A.1

## Relevance

It is important for students to be able to add to 100 crossing ten, so they can determine totals.

## Introduction

Practice by dragging the balloons to where they belong on the number line to 100. Then practice two addition problems on the number line to 50, with and without regrouping.

## Development

First discuss the importance of being able to add to 100 and then discuss how to cross ten. Next the lesson goal is discussed in three ways, visually, in the abstract and in story problems. You can use the menu in the bottom right to determine which method best fits your classroom needs.
Starting with the visual method you start by counting the objects. Next you explain how you add the two together. The next addition problem can be done as a class. Check that students are able to complete the addition problems. For the abstract explanation, students are presented with different ways to calculate the addition problems. Show them how to use the number line to move to the nearest tens number and then count 1 more. Then use the number line to show how to add from 57. Then demonstrate two ways to calculate without the number line. For the story problems, explain the steps of a story problem and then ask students to solve a story problem.

Check that students are able to add to 100 crossing ten with addends less than 10 by asking the following questions:
- Why is it useful to be able to add to 100?
- What do you look at first when adding to 100?
- How do you regroup in an addition problem like 88+4?

## Guided practice

Students first are given an addition problem with visual support, then without visual support, and are then asked to do a story problem.

## Closing

To close the lesson, have students play a game with dice. Ask students to form groups and give each group a 10-sided dice. Each student starts with 50 points and as they roll, they must add the number thrown to their number. The first student to reach 100 ends the game.

## Teaching tips

Students who have difficulty adding to 100 can be supported by the use of manipulatives like blocks, or by drawing every addition problem on the number line.

## Instruction materials

10-sided dice 