Year 1 - Maths
Solve subtraction problems using knowledge of 10 and a bit
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 solve subtraction problems using knowledge of 10 and a bit in different contexts.
Key Notes
- The teens numbers can be represented as ten and a bit.
- We can solve addition and subtraction problems with the ones part or tens part missing.
- A part-part whole model can help to represent the missing whole or missing parts.
Vocabulary To Learn
- Partition: The act of splitting an object or value down into smaller parts.
- Whole: All of a group or number.
- Part: A piece or section of the whole.
Common Mistakes To Avoid
- Pupils do not connect a known partition of a teen number e.g. 16 is 1 ten and 6 ones to a subtraction or addition context and therefore use a less efficient strategy.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
The teens numbers can be represented as ten and a bit. We can solve addition and subtraction problems with the ones part or tens part missing.
2. Use this key word in a maths sentence and explain it clearly. 'Partition'
The act of splitting an object or value down into smaller parts. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils do not connect a known partition of a teen number e.g. 16 is 1 ten and 6 ones to a subtraction or addition context and therefore use a less efficient strategy. Correction: Practical experiences using a group of 10 and ones are key to supporting understanding that the partitioning structure can work for different contexts.
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
- 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
- Use knowledge of subtraction facts within 10 to subtract within 20 Study Guide
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