Addition to 20

General

Students learn to add to 20.

Standards

1.OA.C

Relevance

It is important to be able to add to 20, so you know how many you have together.

Introduction

The interactive whiteboard shows a number sequence to twenty, with four numbers missing. Students must determine what the missing numbers are from the number bank on the right and drag them to their spots in the sequence.

Development

Explain to students how you can add. First is to add by counting. You first count how many you have, that is your first addend, and then you count how many more are joining, your second addend. When you count them together, you get the sum, or total of the two addends together. You can demonstrate this with the dots and cherries on the interactive whiteboard. Check that students understand this by asking them to add the money together. Ask them what total they get. Next, explain how you can add using support from blocks, a rekenrek, or the number line. Explain that it is easy to first make ten before adding the rest of the number. Have students practice this as well. Finally, show them how to solve a story problem. First they determine what kind of problem it is, then which numbers are needed from the story, to say the problem, and then to solve the problem. Have students solve the story problem.

Check that students understand adding to 20 by asking the following questions:
- What is useful if you want to add on the number line?
- What do you look at if you want to solve a story problem?
- How do you calculate the sum of 8+7?

Quiz

Students first practice adding two addends with visual support. Next they are only given the addition problem and must calculate the total. They are then given a story problem. Ask students what the addition problem is and how they solve it.

Closing

Repeat the lesson goal and why it is important. The interactive whiteboard shows a number of baby chicks as well as a nest with baby chicks just hatching. The students must come up with the addition problem that represents the image, and then calculate the total. You can ask students how they determined the problem as well as how they calculated the total. They do the same with the image of glasses of juice.