Year 6 - Maths
Explain and represent constant difference for subtraction
Use equivalence and compensation to simplify and solve subtraction problems
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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 explain how increasing or decreasing the minuend affects the difference and solve subtraction calculations mentally by using known facts explaining how adjusting the minuend can make mental calculation easier.
Lesson Summary
You will learn to explain and represent constant difference for subtraction.
Key Notes
- If the minuend and subtrahend are both increased by the same amount, the difference stays the same.
- If the minuend and subtrahend are both decreased by the same amount, the difference stays the same.
- A number line can be used to represent the 'same difference' generalisation.
Vocabulary To Learn
- Minuend: The minuend is the number being subtracted from.
- Subtrahend: A subtrahend is a number subtracted from another.
- Difference: The difference is the result after subtracting one number from another.
- Constant: A constant is a quantity that has a fixed value that does not change or vary, such as a number.
Common Mistakes To Avoid
- The concept of constant difference is difficult to understand when looking simply at abstract equations and numerals and pupils may find it challenging to 'see' the underlying structure of the maths.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
If the minuend and subtrahend are both increased by the same amount, the difference stays the same. If the minuend and subtrahend are both decreased by the same amount, the difference stays the same.
2. Use this key word in a maths sentence and explain it clearly. 'Minuend'
The minuend is the number being subtracted from. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: The concept of constant difference is difficult to understand when looking simply at abstract equations and numerals and pupils may find it challenging to 'see' the underlying structure of the maths. Correction: Make good use of physical resources to reinforce the idea of constant difference. Number rods coupled with rulers or number lines can be very useful here. Take time with smaller values so pupils can generalise.
More Lessons In This Unit
- Calculate the difference using knowledge of an adjusted subtrahend: difference structure Study Guide
- Explain how adjusting the minuend can make mental calculation easier Study Guide
- Explain how adjusting the subtrahend affects the difference: partitioning Study Guide
- Explain how adjusting the subtrahend affects the difference: reduction structure Study Guide
- Explain how constant difference can make written calculations more efficient Study Guide
- Explain how increasing or decreasing the minuend affects the difference Study Guide
- Solve subtraction calculations mentally by using known facts Study Guide
- Use constant difference to balance equations and find unknowns Study Guide
- Use equivalence and compensation strategies to solve subtraction problems in a range of contexts Study Guide
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