Year 3 - Maths
Subtract from a 3-digit number using column subtraction with regrouping
Column subtraction
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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 identify the minuend and the subtrahend in column subtraction and explain the column subtraction algorithm. They will subtract from a 2-digit number using column subtraction with exchanging.
Lesson Summary
You will learn to subtract from a 3-digit number using column subtraction with regrouping.
Key Notes
- Start with the numbers with the smallest place value first.
- Regroup when the ones or tens digit of the subtrahend is greater than the ones or tens digit of the minuend.
- If the tens digit of the minuend is a zero, a hundred is regrouped before a ten is regrouped.
Vocabulary To Learn
- Column subtraction: Column subtraction is a way of subtracting numbers by writing a number below another.
- Regrouping: The process of unitising and exchanging between place values is known as regrouping.
Common Mistakes To Avoid
- Pupils may struggle to regroup in the ones and tens when the tens digit is zero.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Start with the numbers with the smallest place value first. Regroup when the ones or tens digit of the subtrahend is greater than the ones or tens digit of the minuend.
2. Use this key word in a maths sentence and explain it clearly. 'Column subtraction'
Column subtraction is a way of subtracting numbers by writing a number below another. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils may struggle to regroup in the ones and tens when the tens digit is zero. Correction: Explain that pupils may need to regroup from the hundreds first, and then regroup in the ones. They still need to start with the numbers with the smallest place value. When crossing out, pupils need to cross out the '10' tens and replace with 9.
More Lessons In This Unit
- Identify the minuend and subtrahend in column subtraction Study Guide
- Make efficient use of subtraction strategies including column subtraction Study Guide
- Subtract from a 2-digit number using column subtraction with regrouping Study Guide
- Use column subtraction to subtract from a 2- or 3-digit number Study Guide
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