Primary 1 maths · Operations · About 8 minutes
Connect addition and subtraction with number bonds
Predict, build a model, explain what changed, then use the relationship in a new situation.
Start the interactive lesson →Open practice activity
What you will learn
- Connect addition and subtraction with number bonds
Models used: number sentences, stories, diagrams.
Before you start
Connect the action to the maths
Eight counters belong to one group. Five are blue and three are orange. How can this one picture show both adding and taking away?
The whole is 8. The two branches show the parts that belong to that whole.
Here are our eight counters in two parts. Trace the lines: both parts belong to the same whole.
5 + 3 = 8
8wholepart5part3Start with the whole 8. Take away the right part of 3. The other part stays.
Start with the whole eight. Imagine covering the orange part of three. The blue part of five stays.
8 − 3 = 5
8wholestays5taken away3Start with the whole 8. Take away the left part of 5. The other part stays.
Now uncover the orange part and cover the blue part instead. This time the orange three stay.
8 − 5 = 3
8wholetaken away5stays3The whole is 8. The two branches show the parts that belong to that whole.
Addition joins the parts. Subtraction starts with the whole and finds the other part. We used the same eight counters each time.
5 + 3 = 8; 8 − 3 = 5; 8 − 5 = 3
8wholepart5part3
Worked example: A different whole, the same connection
Nine counters have two parts: six and three. What is 9 − 6?
The whole is 9. The two branches show the parts that belong to that whole.
The whole is now nine. Its parts are six and three. First find the whole and both parts in the picture.
9wholepart6part3Start with the whole 9. Take away the left part of 6. The other part stays.
We take away the part of six. The question asks for the part that stays.
9wholetaken away6stays3Nine counters have two parts: six and three. What is 9 − 6?
3
The whole is 9. The two branches show the parts that belong to that whole.
Three stays. Put the six back and the whole becomes nine again.
9 − 6 = 3; 3 + 6 = 9
9wholepart6part3
Common mistakes to discuss
- A part as large as the whole. The two parts must together make the whole. For a whole of 8, parts of 5 and 3 work; 8 and 5 do not.
Check your understanding
- Use the same whole and two parts to explain adding and taking away.
- connect whole-and-part pictures with addition and subtraction
- check the answer against the original quantities and units
Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.
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