Addition to 100 with tens

General

Students learn to add numbers to 100 with tens.

Common core standard(s)

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

Relevance

Discuss with students that it is important to be able to add numbers to 100, so you know how much you have together.

Introduction

Show students the hands on the interactive whiteboard and ask if they can determine the addition problem shown by the hands. Tell students that it is an addition problem using the zero rule. Ask two students to come to the front of the class and create an addition problem using the zero rule as well. The class must guess what the addition problem is that the students are showing.

Development

Explain that tens always end in 0. Next explain to the class that you can add amounts by counting the gorups. You first count how many you have, this is the first addend of the addition problem. Next you count how many objects are being added, that's the second addend of the addition problem. Their total is the final combined amount together. Show this on the interactive whiteboard with the blocks and eggs. Check that students understand with the next exercises. Next, explain that you can add problems in different ways. Explain that you can make use of a number line. You can also split the second addend into different parts, you can swap the addends, you can first add tens and then add ones, or you can add it all at once in your head. Emphasize to students that they should take a close look at the addition problem to determine which method they want to use. Ask students which method they use for a problem. Finally show students how to solve a story problem. Give them the steps of solving a story problem, namely determining which numbers are needed for the problem, saying or writing the problem, solving the problem and finding the total. Ask students to solve a story problem.

Check that students can add to 100 with tens by asking the following questions:
- What do you look at when you want to solve a story problem?
- How do you calculate 58+20 and 30+10?

Guided practice

Students first practice adding to 100 with visual support. Next they are given the addition problem without visual support, and finally they are given a story problem to solve.

Closing

Discuss with students that it is important to be able to add to 100, so they can solve addition problems and determine amounts. Show a few images on the interactive whiteboard and ask students which addition problems match the images. Have students then solve the problems. Finally ask students to come up with story problems in pairs to match the numbers given on the board. Ask them to solve the story problems.