Year 2 - Maths
Use knowledge of calculating within 20 to solve problems
Calculating within 20
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Study Guides
This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils will add 3 addends. They will use a strategy such as finding 2 addends to total 10 or 2 numbers to bridge though 10.
Lesson Summary
You will learn to use knowledge of calculating within 20 to solve problems in a range of contexts.
Key Notes
- When adding three addends, it is efficient to first add two addends using a known fact e.g. pair to 10 or double.
- When adding, we can bridge 10 by partitioning a part so that we can 'make 10'.
- When subtracting, we can bridge 10 by partitioning a part to create a part that is equal to the ones digit of whole.
- The difference can be found through subtraction.
Vocabulary To Learn
- Visualise: To imagine a given problem before us in real life.
- Represent: To communicate mathematical ideas through models.
- Calculate: To choose one of the four operations to solve a problem.
- Efficient: Not wasting time or effort. An efficient strategy is one we can carry out easily.
Common Mistakes To Avoid
- Without correct representation, children may struggle to know what to calculate.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
When adding three addends, it is efficient to first add two addends using a known fact e.g. pair to 10 or double. When adding, we can bridge 10 by partitioning a part so that we can 'make 10'.
2. Use this key word in a maths sentence and explain it clearly. 'Visualise'
To imagine a given problem before us in real life. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Without correct representation, children may struggle to know what to calculate. Correction: If needed, provide support at this stage so that the structure of the mathematics is clear to children.
More Lessons In This Unit
- Add and subtract two numbers that bridge through 10 Study Guide
- Add three addends Study Guide
- Add three addends efficiently Study Guide
- Add three addends efficiently by finding two addends that total 10 Study Guide
- Add two numbers that bridge through 10 Study Guide
- Calculate the difference Study Guide
- Calculate the difference in different contexts Study Guide
- Calculate the difference when information is presented in a bar chart Study Guide
- Calculate the difference when information is presented in a pictogram Study Guide
- Compare the number of objects in two sets or difference between two measures. Study Guide
- Explain that the addends can be added in any order Study Guide
- Explain what the difference is between consecutive numbers Study Guide
- Use a 'First, then, then, now' story to add three addends Study Guide
- Use knowledge of calculating within 20 to solve problems involving statistics Study Guide
Browse all guides in the Year 2 Maths guide library.