Addition to 20

General

Students learn to add numbers to 20, without carrying numbers.

Relevance

It is important that you are able to add numbers to twenty, so you know how many objects you have when two groups of objects are joined.

Introduction

The interactive whiteboard shows a number line from 0 to 20 with a question mark somewhere on the number line. There are 3 markers with numbers. The students must determine which marker belongs at the question mark. You can ask students how they determine which marker has the correct number.

Development

Explain that you add by counting amounts. You first count how many you already have, that is the first addend. Next, you count how many more are being added, which is the second addend in the addition problem. When you find the total of those two numbers, you have the answer.You can demonstrate this on the interactive whiteboard with the dots and strawberries. Check that students are able to do this by asking them to add the hands and money. Ask students what the addition problem is that they solved. Explain that you can add using blocks, a rekenrek, or a number line. Have students practice this themselves. Finally, show how you can solve a story problem. Have students determine what the addition problem is, which numbers it is made up of and what the addition problem is, and what the total is. Let the students solve another story problem.

To check that students can add up to twenty without carrying numbers, you can ask the following questions:
What do you do 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 14+3?

Guided practice

Students first practice adding two addends to 20 using visual support. Next they get an addition problem without the visual support. Students also get a story problem to solve. Ask students how they solve this type of problem.

Closing

Repeat the goal of being able to add to 20 and why it is important. On the interactive whiteboard there is a piggy bank with an amount of money and a hand with some money. The students must determine which addition problem matches the image and must calculate the total. You can ask students which method they used and why they like this one best.