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What is a part-whole model?

This is a part-whole model.

A part-whole model has two parts.

Sometimes a part-whole model looks different but every time the part-whole has two parts that add up to the whole.

Example 1

Here is a part-whole model. It shows you how a number can be made by adding two other numbers together.

How many stars should you put in the missing part?

✓ The missing part is 3 stars.

Let's complete the model. 3 stars should be added to show the value of the missing part.

Like this:

We can check this by doing the calculation:

4 - 1 = 3

This shows that when the whole is 4 and one of the parts is 1, the other part must be 3.

Example 2

Here is another part-whole model. The whole is 8 and one of the parts is 3.

What number is the missing part?

✓ The missing part is 5.

The completed part-whole model shows the calculation:

8 - 3 = 5

Can you see that it could also show:

• 8 - 5 = 3
• 5 + 3 = 8
• 3 + 5 = 8

Example 3

Here is another part-whole model. The parts are 8 and 2.

What is the whole?

✓ The whole is 10.

This part-whole model shows:

• 8 + 2 = 10
• 2 + 8 = 10
• 10 - 2 = 8
• 10 - 8 = 2

Activity 1

Use what you've learned about part-whole models to find the missing numbers in this quiz.

Activity 2

Practise your addition skills in this quiz.