Decomposing numbers to 10

Decomposing numbers to 10

Decomposing numbers to 10

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Decomposing numbers to 10

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Students learn to decompose amounts to 10 in different ways by dividing objects in various ways.


It is important to be able to do this so you know how to divide something. An example: splitting sugar cubes between a big horse and a little horse. The big horse gets more sugar cubes than the little horse.


Students practice composing amounts to 10 by dragging glasses of juice to create the given numbers.


Give each student 6 blocks and tell them that they are going to divide the blocks into two groups. This is called decomposing. You can divide your blocks in different ways. Show the possible divisions by example on the interactive whiteboard. Say that each decomposed number can also switch numbers in the number bond. So 6 can be decomposed into 5 and 1, but also 1 and 5. Ask the students to decide which of the shown images show a decomposed 6, decomposed 7 or 9 using cookies and cars as examples.

Check that students understand decomposing to 10 by asking the following questions:
- What does decomposing mean?
- Are there more things in the class we could decompose?
- When is it useful to be able to split things?

Guided Practice

Students practice decomposing by counting the total number of objects in the image. They then need to choose two images which are decompositions of the same number.


Ask students to practice decomposing 10 blocks in pairs. Say that they have to make different decompositions for the numbers you give them.

Teaching Tip

Students who have difficulty can practice composing to 10. Students who need more challenge can be encouraged to do decomposition in their heads.

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