Decomposing and composing 2 to 9

General

Students learn to decompose and compose the numbers 2 to 9. They learn to recognize decomposition in images, but also using arrows and number bonds. They learn to compose numbers by counting.

Introduction

Students practice counting to 10 by counting objects on the interactive whiteboard and writing the numbers.

Instruction

You can decompose numbers in different ways. Using the image of cookies, explain that you can divide the number 8 into 4 and 4, but also into 6 and 2, and this is called decomposing numbers. If you already have one of the numbers, you can count on to see how many are needed to reach the number, this is called composing numbers. Show decompositions by showing the different ways in which 6 cookies can be split between two plates. Show all decompositions of 6. Explain that you can switch the numbers in a number bond. You can also use an arrow to decompose the number.

Practice recognizing numbers in the images with beads and discuss which numbers they can switch and how to write the number bonds with arrows. Explain to students that if the decomposition isn't clear from the colors then they need to count. Practice this together and make sure that for composing numbers they know to count on. There are also decompositions without any objects. Encourage students to make the decomposition in their heads, but allow students to use blocks for support if desired.

Check that students understand decomposing and composing the numbers 2-9 by asking the following questions:
- What is decomposing? and composing?
- How can you check if your number bond is correct? (count the total)
- Can you give examples of how you could decompose the number 8?

Guided Practice

Students first practice decomposing numbers using images of beads in two colors. Next, they decompose a number where they need to count by themselves, and finally, they get a number without any images as support.

Closing

Students practice decomposing and composing numbers to 9 in pairs. Ask one student to set down a random amount of blocks, and the second student must compose 9. Take turns. Ask them to compose the numbers on the interactive whiteboard and write down their answers. Check the answers as a class. Discuss together why it is useful to be able to decompose and compose so you know in which different ways you can divide something.