Year 3 - Maths
Subtract a pair of 2-digit numbers by finding the difference
Informal and mental strategies for adding and subtracting two 3-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 will add and subtract two 3-digit numbers using partitioning, adjusting, redistribution and bridging.
Lesson Summary
You will learn to subtract a pair of 2-digit numbers by finding the difference.
Key Notes
- When the minuend and subtrahend are close in value, finding the difference can be an efficient strategy for subtraction
- Finding the difference means we count on from the subtrahend or count back from the minuend
- A number line or a bar model can represent finding the difference
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.
Common Mistakes To Avoid
- Pupils will often try to use a written method/algorithm which they know gives an accurate answer but don't understand why it works.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
When the minuend and subtrahend are close in value, finding the difference can be an efficient strategy for subtraction. Finding the difference means we count on from the subtrahend or count back from the minuend.
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: Pupils will often try to use a written method/algorithm which they know gives an accurate answer but don't understand why it works. Correction: Encourage the pupils to be brave and remind them that this is about mental subtraction so, with practice, will be quicker than any written methods.
More Lessons In This Unit
- Add 2 and 3-digit numbers by redistributing Study Guide
- Add two 3-digit numbers using adjusting strategies Study Guide
- Add two 3-digit numbers using partitioning Study Guide
- Choose the most efficient strategy to add two 3-digit numbers Study Guide
- Choose the most efficient strategy to subtract from a 3-digit number Study Guide
- Subtract 2 or 3-digit numbers using partitioning and bridging a multiple of 10 Study Guide
- Subtract 3-digit multiples of 10 by finding the difference between them Study Guide
- Use addition and subtraction to solve problems in different contexts Study Guide
- Use addition and subtraction to solve problems involving bar charts, pictograms and tables Study Guide
Browse all guides in the Year 3 Maths guide library.