Year 5 - Maths
Multiply a 3-digit by a 1-digit number with one or two regroups
Multiplication by partitioning leading to short multiplication (3 by 1-digit)
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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 multiply a 3-digit number by a single-digit number using expanded and short multiplication.
Lesson Summary
You will learn to multiply a 3-digit by a 1-digit number using expanded and short multiplication (one or two regroups).
Key Notes
- If the product of the ones digits is greater than 10 then you regroup ten ones into one ten.
- If the product of the 1-digit number and the tens digit is greater than 100 then you regroup ten 10s into one 100
- If the product of the 1-digit number and the 100s digit is greater than 1,000 then you regroup ten 100s into one 1,000
Vocabulary To Learn
- Regroup: The process of unitising and exchanging between place values is known as regrouping.
- Expanded multiplication: A way of recording the steps of a calculation focusing on partitioning one or more factors and showing partial products.
- Short multiplication: A way of recording using columns to set out and calculate a multiplication.
Common Mistakes To Avoid
- Children may misalign digits when arranging into the short multiplication layout.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
If the product of the ones digits is greater than 10 then you regroup ten ones into one ten. If the product of the 1-digit number and the tens digit is greater than 100 then you regroup ten 10s into one 100.
2. Use this key word in a maths sentence and explain it clearly. 'Regroup'
The process of unitising and exchanging between place values is known as regrouping. 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 misalign digits when arranging into the short multiplication layout. Correction: Children should use unitising language to help them understand and apply this to formal written methods.
More Lessons In This Unit
Browse all guides in the Year 5 Maths guide library.