Year 2 - Maths
Combine tens and ones within equations
Addition and subtraction of two 2-digit numbers
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils apply their knowledge of known facts and understanding of place value to add and subtract with 2-digit numbers both within and across the tens boundary.
Lesson Summary
You will learn to combine and partition tens and ones in the context of equations.
Key Notes
- Known strategies can be used to help us prepare for the addition of two 2-digit numbers.
- It is important to be able to calculate mentally before adding two 2-digit numbers.
Vocabulary To Learn
- Calculate: To work out an answer, often by adding or subtracting.
- Efficiently: Not wasting time or effort. An efficient strategy is one we can carry out easily.
Common Mistakes To Avoid
- Children may rely on the order of the addends rather than their place value when calculating. They may also default to counting on rather than using known facts.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Known strategies can be used to help us prepare for the addition of two 2-digit numbers. It is important to be able to calculate mentally before adding two 2-digit numbers.
2. Use this key word in a maths sentence and explain it clearly. 'Calculate'
To work out an answer, often by adding or subtracting. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Children may rely on the order of the addends rather than their place value when calculating. They may also default to counting on rather than using known facts. Correction: Refer back to known facts and efficient strategies and model their use throughout, discussing the best strategy to use at each point and why. Model errors that can be made when not adding ones then tens for example, or in counting on in ones.
More Lessons In This Unit
- Add 2-digit numbers when crossing the tens boundary Study Guide
- Add two-digit numbers without crossing the tens boundary Study Guide
- Create addition and subtraction problems Study Guide
- Explain different strategies used to subtract Study Guide
- Find the missing addend when adding two-digit numbers Study Guide
- Find the missing part when subtracting two-digit numbers Study Guide
- Solve equations involving the subtraction of two-digit numbers Study Guide
- Solve problems involving addition and subtraction Study Guide
- Solve problems involving subtraction of two-digit numbers Study Guide
- Solve problems involving subtraction when bridging 10 Study Guide
- Solve problems involving the addition of two-digit numbers Study Guide
- Subtract two-digit numbers crossing the tens boundary Study Guide
- Use efficient addition strategies to calculate Study Guide
- Use efficient methods to solve subtraction equations Study Guide
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