Year 1 - Maths
Use knowledge of subtraction facts within 10 to subtract within 20
Composition of numbers 11 to 19
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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 will explain 11-19 as cardinal and ordinal numbers. They will double and halve numbers 6-9 and use addition and subtraction facts to add and subtract within 20.
Lesson Summary
You will learn to use knowledge of subtraction facts within 10 to subtract within 20.
Key Notes
- Subtraction facts within ten can be applied to subtraction within 20, e.g. if 5 - 2 = 3 then 15 - 2 = 13
- A number line can be used to show the link between subtraction of one-digit numbers and teen numbers.
Vocabulary To Learn
- Subtraction: To partition one part from another (the subtrahend from the difference), or to decrease an amount by taking an amount away.
- Minus: A synonym for subtract, represented by the symbol -
- Difference: The result of subtracting one number from another. How much one number differs from another.
Common Mistakes To Avoid
- Children may rely on counting strategies instead of using known facts to subtract from larger numbers.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Subtraction facts within ten can be applied to subtraction within 20, e.g. if 5 - 2 = 3 then 15 - 2 = 13. A number line can be used to show the link between subtraction of one-digit numbers and teen numbers.
2. Use this key word in a maths sentence and explain it clearly. 'Subtraction'
To partition one part from another (the subtrahend from the difference), or to decrease an amount by taking an amount away. 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 counting strategies instead of using known facts to subtract from larger numbers. Correction: Make comparisons between subtraction within 10 and within 20, looking for patterns. Make sure children notice that the ones digit stays the same when we subtract numbers with the same ones digits such as 5 - 2 and 15 - 2.
More Lessons In This Unit
- Double the numbers 6 to 9 and halve the result explaining what doubling and halving is Study Guide
- Explain that the digits in the numbers 11 to 19 express position on a number line Study Guide
- Explain that the digits in the numbers 11 to 19 express quantity Study Guide
- Explore odd and even numbers within 20 Study Guide
- Identify the quantity shown in a representation of numbers 11 to 19 Study Guide
- Solve subtraction problems using knowledge of 10 and a bit Study Guide
- Use knowledge of 10 and a bit to solve problems Study Guide
- Use knowledge of addition and subtraction facts within 10 to add and subtract within 20 Study Guide
- Use knowledge of addition facts within 10 to add within 20 Study Guide
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