 # Addition through 100 with tens

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## General

Students learn to add through 100 with tens.

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## Relevance

It is important to learn how to add beyond 100 using tens, so you can quickly add larger numbers together. An example is when you want to add large money amounts together.

## Introduction

The interactive whiteboard shows a frog in a lake that is jumping around. Each jump is ten. The students must fill in the blanks of the frog's jumps. Students must then skip count in 10s as a class, with one student starting with ten, the next to say 20, etc on to 100. You can choose to start again or to have them skip count backwards in 10s back to zero.

## Development

Start by showing students how to add larger groups, namely by counting in groups of ten. Explain that you start by counting how many you already have, then counting how many more are being added, and then adding them together. You can repeat this with the ten frames. Next explain to students that when you count in tens and go through 100, the tens changes into a hundreds, and a third digit is added. Show this on the number line. Then tell students that it can be helpful to first add to 100, and then to add the rest. Do this together with the students on an empty number line. Finally explain to students which steps to take in solving a story problem. Walk through the steps of solving a story problem- what kind of math problem is it, which numbers do you need, to say or write the math problem, and finally to calculate the math problem. You can practice this with the story problem about cans.

To check that students understand addition through 100 with tens you can ask the following questions:
- What is useful to do as a first step when adding beyond 100 in tens?
- How do you know how much more you need to add once you've added to 100?
- What must you watch our for when doing a story problem?

## Guided practice

Students first practice adding through 100 with visual support. Then they are asked to add without visual support and finally are asked to solve a story problem. Encourage students to first add to 100 and then to add the rest.

## Closing

Repeat the goal of the lesson and why it is important. The interactive whiteboard has 5 ice cream cones. Each scoop of ice cream contains a number, and each cone contains an answer. Students must calculate and determine if the answers in the cones are correct or incorrect. You can ask the class to give a thumbs up or down for each answer.

## Teaching tips

If students have difficulties adding through 100 with tens, encourage them to draw the steps on a number line. Have them add to 100 first on the number line and then continue on past 100. 