 # Addition to 1,000 via simplification

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## General

Students learn that you can use a simplified addition problem to use as a first step to solving a more difficult addition problem. If you know the total of an addition problem without the hundreds, you can quickly determine the answer with hundreds.

2.NBT.B.7

## Relevance

It is important to learn this, to make calculating large numbers quicker and easier.

## Introduction

Start by creating numbers with the three given digits. You can make 6 numbers with the given digits. Ask students to try to find all 6 in groups. Then ask which created number is the greatest, and which is the least. Next, give them a pop quiz with addition problems to 100 with and without regrouping.

## Development

Check that students understand addition to 1,000 using simplification by asking the following questions:
- 46+2=18, 146+2= ?
- 4+9=13, 304+9= 313. How do you know this?
- 28+13=41, Which addition problem can you now easily solve?

## Guided practice

Students first practice with addition problems in which 100 is added to the first step. Then students are given addition problems with random amounts of hundreds added.

## Closing

Repeat why it is important to learn how to simplify while adding to 1,000. It helps you solve large addition problems easily and quickly. If you can solve the problem without the hundreds then you will also be able to solve the problem with hundreds. Check that students have understood by asking students to solve an addition problem with visual support, as well as a few without visual support.

## Teaching tips

Make the method of simplification visual for students by having them work with MAB blocks or with money. Give them a 20 dollar bill and a 10 dollar bill. They know that 20+10=30. If you give them a 100 dollar bill, then they get 110=20=130. And if they get a second hundred dollar bill it is 210+20=230. And if they get yet another hundred dollar bill it is 310+20=330. Repeat this with different amounts. Make sure to point out that they do not need to recalculate the addition problem with hundreds, because they already know what the total should be by having the total of the first step.

## Instruction materials

Optional: MAB-blocks or money 