🎓 Year 3 (ACARA Code : AC9M3A01)
🎯Focus:
⭐ recognise addition and subtraction as opposite operations.
⭐ use subtraction to find a missing part in an addition sentence.
⭐ use addition to check a subtraction answer.
⭐ solve simple number sentences with an unknown value.
⭐ explain how inverse operations help find missing numbers.
Video Lessons
📹 Video Lesson Tips
- Before
- 🔢 Show a number sentence with a missing box.
- 👀 Ask children what might be missing.
- ✋ Revise add, subtract, total, and difference.
- During
- ➕ Show how addition and subtraction undo each other.
- 🧠 Pause and let children solve the missing number.
- ⭐ Use number lines, counters, or arrows to help.
- After
- 📝 Ask children to make their own missing-number sentence.
- 🎨 Let them draw counters to check the answer.
- 📣 Review the word inverse.
💡 Key Ideas (Quick Guide)
✏️ Inverse operations are opposites that help us solve missing numbers.
📌 Important words
- Unknown = the missing number
- Inverse = the opposite operation
- Check = use the other operation to make sure the answer is right
- Total = the answer in an addition sentence
➕➖ How it works
- If a number is missing in addition, use subtraction.
- If a number is missing in subtraction, use addition.
- Use the known numbers to work out the missing one.
✨ Remember
🧠 Counters and number lines can help.
🧠 Addition and subtraction are linked.
🧠 You can solve and check your answers.
🧩 Mini Quiz – Quick Check
Try these after watching the video:
❓Question 1:What is a missing number called?
✅ Answer: Unknown
❓Question 2:Which operation is the opposite of addition?
✅ Answer: Subtraction
❓Question 3: If 7 + ? = 10, what can you do to find ?
✅ Answer: Subtract 7 from 10
❓Question 4: What can help you solve missing numbers?
✅ Answer: Counters
❓Question 5: What does “inverse” mean?
✅ Answer: Opposite
Scored:
5/5 💯 = Champion!
3–4/5 🌟 = Great Work!
0–2/5 🔄 = Watch the video again!
📄 Sample Worksheet Preview
📥 Download Free Printable 6 Worksheet Pack
🎉 The preview above is just 1 sample.
Sign up with your email to receive the full pack of 6 worksheets.
📚 Other Lessons in This Unit
🚀 Learning Path (Recommended Order)
| Step | 🔗 Lesson | 💡 What You Learn |
|---|---|---|
| 1️⃣ | 🔢Partitioning Numbers, Part-Part-Whole and Bar Models | Practise partitioning numbers and learn reading bar models |
| 2️⃣ | ✏️Inverse Operations in Year 3: Finding Unknown Numbers ⭐ You are here⭐ | Use fact families to find unknown numbers in equations and check answers by working backwards. |
| 3️⃣ | 🧩 Inverse Operations: Connecting Addition and Subtraction | Deepen their understanding of inverse operations by connecting mental addition and subtraction |